# Upgrading from AngularJS to Angular

_Angular_ is the name for the Angular of today and tomorrow.<br />
_AngularJS_ is the name for all 1.x versions of Angular.

AngularJS apps are great.
Always consider the business case before moving to Angular.
An important part of that case is the time and effort to get there.
This guide describes the built-in tools for efficiently migrating AngularJS projects over to the
Angular platform, a piece at a time.

Some applications will be easier to upgrade than others, and there are
many ways to make it easier for yourself. It is possible to
prepare and align AngularJS applications with Angular even before beginning
the upgrade process. These preparation steps are all about making the code
more decoupled, more maintainable, and better aligned with modern development
tools. That means in addition to making the upgrade easier,
you will also improve the existing AngularJS applications.

One of the keys to a successful upgrade is to do it incrementally,
by running the two frameworks side by side in the same application, and
porting AngularJS components to Angular one by one. This makes it possible
to upgrade even large and complex applications without disrupting other
business, because the work can be done collaboratively and spread over
a period of time. The `upgrade` module in Angular has been designed to
make incremental upgrading seamless.

## Preparation

There are many ways to structure AngularJS applications. When you begin
to upgrade these applications to Angular, some will turn out to be
much more easy to work with than others. There are a few key techniques
and patterns that you can apply to future proof apps even before you
begin the migration.

{@a follow-the-angular-styleguide}

### Follow the AngularJS Style Guide

The [AngularJS Style Guide](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md)
collects patterns and practices that have been proven to result in
cleaner and more maintainable AngularJS applications. It contains a wealth
of information about how to write and organize AngularJS code - and equally
importantly - how **not** to write and organize AngularJS code.

Angular is a reimagined version of the best parts of AngularJS. In that
sense, its goals are the same as the AngularJS Style Guide's: To preserve
the good parts of AngularJS, and to avoid the bad parts. There's a lot
more to Angular than just that of course, but this does mean that
*following the style guide helps make your AngularJS app more closely
aligned with Angular*.

There are a few rules in particular that will make it much easier to do
*an incremental upgrade* using the Angular `upgrade/static` module:

* The [Rule of 1](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#single-responsibility)
  states that there should be one component per file. This not only makes
  components easy to navigate and find, but will also allow us to migrate
  them between languages and frameworks one at a time. In this example application,
  each controller, component, service, and filter is in its own source file.

* The [Folders-by-Feature Structure](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#folders-by-feature-structure)
  and [Modularity](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#modularity)
  rules define similar principles on a higher level of abstraction: Different parts of the
  application should reside in different directories and NgModules.

When an application is laid out feature per feature in this way, it can also be
migrated one feature at a time. For applications that don't already look like
this, applying the rules in the AngularJS style guide is a highly recommended
preparation step. And this is not just for the sake of the upgrade - it is just
solid advice in general!

### Using a Module Loader

When you break application code down into one component per file, you often end
up with a project structure with a large number of relatively small files. This is
a much neater way to organize things than a small number of large files, but it
doesn't work that well if you have to load all those files to the HTML page with
&lt;script&gt; tags. Especially when you also have to maintain those tags in the correct
order. That's why it's a good idea to start using a *module loader*.

Using a module loader such as [SystemJS](https://github.com/systemjs/systemjs),
[Webpack](http://webpack.github.io/), or [Browserify](http://browserify.org/)
allows us to use the built-in module systems of TypeScript or ES2015.
You can use the `import` and `export` features that explicitly specify what code can
and will be shared between different parts of the application. For ES5 applications
you can use CommonJS style `require` and `module.exports` features. In both cases,
the module loader will then take care of loading all the code the application needs
in the correct order.

When moving applications into production, module loaders also make it easier
to package them all up into production bundles with batteries included.

### Migrating to TypeScript

If part of the Angular upgrade plan is to also take TypeScript into use, it makes
sense to bring in the TypeScript compiler even before the upgrade itself begins.
This means there's one less thing to learn and think about during the actual upgrade.
It also means you can start using TypeScript features in your AngularJS code.

Since TypeScript is a superset of ECMAScript 2015, which in turn is a superset
of ECMAScript 5, "switching" to TypeScript doesn't necessarily require anything
more than installing the TypeScript compiler and renaming files from
`*.js` to `*.ts`. But just doing that is not hugely useful or exciting, of course.
Additional steps like the following can give us much more bang for the buck:

* For applications that use a module loader, TypeScript imports and exports
  (which are really ECMAScript 2015 imports and exports) can be used to organize
  code into modules.

* Type annotations can be gradually added to existing functions and variables
  to pin down their types and get benefits like build-time error checking,
  great autocompletion support and inline documentation.

* JavaScript features new to ES2015, like arrow functions, `let`s and `const`s,
  default function parameters, and destructuring assignments can also be gradually
  added to make the code more expressive.

* Services and controllers can be turned into *classes*. That way they'll be a step
  closer to becoming Angular service and component classes, which will make
  life easier after the upgrade.

### Using Component Directives

In Angular, components are the main primitive from which user interfaces
are built. You define the different portions of the UI as components and
compose them into a full user experience.

You can also do this in AngularJS, using *component directives*. These are
directives that define their own templates, controllers, and input/output bindings -
the same things that Angular components define. Applications built with
component directives are much easier to migrate to Angular than applications
built with lower-level features like `ng-controller`,  `ng-include`, and scope
inheritance.

To be Angular compatible, an AngularJS component directive should configure
these attributes:

* `restrict: 'E'`. Components are usually used as elements.
* `scope: {}` - an isolate scope. In Angular, components are always isolated
  from their surroundings, and you should do this in AngularJS too.
* `bindToController: {}`. Component inputs and outputs should be bound
  to the controller instead of using the `$scope`.
* `controller` and `controllerAs`. Components have their own controllers.
* `template` or `templateUrl`. Components have their own templates.

Component directives may also use the following attributes:

* `transclude: true/{}`, if the component needs to transclude content from elsewhere.
* `require`, if the component needs to communicate with some parent component's
  controller.

Component directives **should not** use the following attributes:

* `compile`. This will not be supported in Angular.
* `replace: true`. Angular never replaces a component element with the
  component template. This attribute is also deprecated in AngularJS.
* `priority` and `terminal`. While AngularJS components may use these,
  they are not used in Angular and it is better not to write code
  that relies on them.

An AngularJS component directive that is fully aligned with the Angular
architecture may look something like this:

<code-example path="upgrade-module/src/app/hero-detail.directive.ts" header="hero-detail.directive.ts">
</code-example>

AngularJS 1.5 introduces the [component API](https://docs.angularjs.org/api/ng/type/angular.Module#component)
that makes it easier to define component directives like these. It is a good idea to use
this API for component directives for several reasons:

* It requires less boilerplate code.
* It enforces the use of component best practices like `controllerAs`.
* It has good default values for directive attributes like `scope` and `restrict`.

The component directive example from above looks like this when expressed
using the component API:

<code-example path="upgrade-module/src/app/upgrade-io/hero-detail.component.ts" region="hero-detail-io" header="hero-detail.component.ts">
</code-example>

Controller lifecycle hook methods `$onInit()`, `$onDestroy()`, and `$onChanges()`
are another convenient feature that AngularJS 1.5 introduces. They all have nearly
exact [equivalents in Angular](guide/lifecycle-hooks), so organizing component lifecycle
logic around them will ease the eventual Angular upgrade process.

## Upgrading with ngUpgrade

The ngUpgrade library in Angular is a very useful tool for upgrading
anything but the smallest of applications. With it you can mix and match
AngularJS and Angular components in the same application and have them interoperate
seamlessly. That means you don't have to do the upgrade work all at once,
since there's a natural coexistence between the two frameworks during the
transition period.

### How ngUpgrade Works

One of the primary tools provided by ngUpgrade is called the `UpgradeModule`.
This is a module that contains utilities for bootstrapping and managing hybrid
applications that support both Angular and AngularJS code.

When you use ngUpgrade, what you're really doing is *running both AngularJS and
Angular at the same time*. All Angular code is running in the Angular
framework, and AngularJS code in the AngularJS framework. Both of these are the
actual, fully featured versions of the frameworks. There is no emulation going on,
so you can expect to have all the features and natural behavior of both frameworks.

What happens on top of this is that components and services managed by one
framework can interoperate with those from the other framework. This happens
in three main areas: Dependency injection, the DOM, and change detection.

#### Dependency Injection

Dependency injection is front and center in both AngularJS and
Angular, but there are some key differences between the two
frameworks in how it actually works.

<table>
  <tr>
    <th>
      AngularJS
    </th>
    <th>
      Angular
    </th>
  </tr>
  <tr>
    <td>
      Dependency injection tokens are always strings
    </td>
    <td>

      Tokens [can have different types](guide/dependency-injection).
      They are often classes. They may also be strings.

    </td>
  </tr>
  <tr>
    <td>

      There is exactly one injector. Even in multi-module applications,
      everything is poured into one big namespace.

    </td>
    <td>

      There is a [tree hierarchy of injectors](guide/hierarchical-dependency-injection),
      with a root injector and an additional injector for each component.

    </td>
  </tr>
</table>

Even accounting for these differences you can still have dependency injection
interoperability. `upgrade/static` resolves the differences and makes
everything work seamlessly:

* You can make AngularJS services available for injection to Angular code
  by *upgrading* them. The same singleton instance of each service is shared
  between the frameworks. In Angular these services will always be in the
  *root injector* and available to all components.

* You can also make Angular services available for injection to AngularJS code
  by *downgrading* them. Only services from the Angular root injector can
  be downgraded. Again, the same singleton instances are shared between the frameworks.
  When you register a downgraded service, you must explicitly specify a *string token* that you want to
  use in AngularJS.

<figure>
  <img src="generated/images/guide/upgrade/injectors.png" alt="The two injectors in a hybrid application">
</figure>

#### Components and the DOM

In the DOM of a hybrid ngUpgrade application are components and
directives from both AngularJS and Angular. These components
communicate with each other by using the input and output bindings
of their respective frameworks, which ngUpgrade bridges together. They may also
communicate through shared injected dependencies, as described above.

The key thing to understand about a hybrid application is that every element in the DOM is owned by exactly one of the two frameworks.
The other framework ignores it. If an element is
owned by AngularJS, Angular treats it as if it didn't exist,
and vice versa.

So normally a hybrid application begins life as an AngularJS application,
and it is AngularJS that processes the root template, e.g. the index.html.
Angular then steps into the picture when an Angular component is used somewhere
in an AngularJS template. That component's template will then be managed
by Angular, and it may contain any number of Angular components and
directives.

Beyond that, you may interleave the two frameworks.
You always cross the boundary between the two frameworks by one of two
ways:

1. By using a component from the other framework: An AngularJS template
   using an Angular component, or an Angular template using an
   AngularJS component.

2. By transcluding or projecting content from the other framework. ngUpgrade
    bridges the related concepts of AngularJS transclusion and Angular content
    projection together.

<figure>
  <img src="generated/images/guide/upgrade/dom.png" alt="DOM element ownership in a hybrid application">
</figure>

Whenever you use a component that belongs to the other framework, a
switch between framework boundaries occurs. However, that switch only
happens to the elements in the template of that component. Consider a situation
where you use an Angular component from AngularJS like this:

<code-example language="html" escape="html">
  &lt;a-component&gt;&lt;/a-component&gt;
</code-example>

The DOM element `<a-component>` will remain to be an AngularJS managed
element, because it's defined in an AngularJS template. That also
means you can apply additional AngularJS directives to it, but *not*
Angular directives. It is only in the template of the `<a-component>`
where Angular steps in. This same rule also applies when you
use AngularJS component directives from Angular.

#### Change Detection

The `scope.$apply()` is how AngularJS detects changes and updates data bindings.
After every event that occurs, `scope.$apply()` gets called. This is done either
automatically by the framework, or manually by you.

In Angular things are different. While change detection still
occurs after every event, no one needs to call `scope.$apply()` for
that to happen. This is because all Angular code runs inside something
called the [Angular zone](api/core/NgZone). Angular always
knows when the code finishes, so it also knows when it should kick off
change detection. The code itself doesn't have to call `scope.$apply()`
or anything like it.

In the case of hybrid applications, the `UpgradeModule` bridges the
AngularJS and Angular approaches. Here's what happens:

* Everything that happens in the application runs inside the Angular zone.
  This is true whether the event originated in AngularJS or Angular code.
  The zone triggers Angular change detection after every event.

* The `UpgradeModule` will invoke the AngularJS `$rootScope.$apply()` after
  every turn of the Angular zone. This also triggers AngularJS change
  detection after every event.

<figure>
  <img src="generated/images/guide/upgrade/change_detection.png" alt="Change detection in a hybrid application">
</figure>

In practice, you do not need to call `$apply()`,
regardless of whether it is in AngularJS on Angular. The
`UpgradeModule` does it for us. You *can* still call `$apply()` so there
is no need to remove such calls from existing code. Those calls just trigger
additional AngularJS change detection checks in a hybrid application.

When you downgrade an Angular component and then use it from AngularJS,
the component's inputs will be watched using AngularJS change detection.
When those inputs change, the corresponding properties in the component
are set. You can also hook into the changes by implementing the
[OnChanges](api/core/OnChanges) interface in the component,
just like you could if it hadn't been downgraded.

Correspondingly, when you upgrade an AngularJS component and use it from Angular,
all the bindings defined for the component directive's `scope` (or `bindToController`)
will be hooked into Angular change detection. They will be treated
as regular Angular inputs. Their values will be written to the upgraded component's
scope (or controller) when they change.

### Using UpgradeModule with Angular _NgModules_

Both AngularJS and Angular have their own concept of modules
to help organize an application into cohesive blocks of functionality.

Their details are quite different in architecture and implementation.
In AngularJS, you add Angular assets to the `angular.module` property.
In Angular, you create one or more classes adorned with an `NgModule` decorator
that describes Angular assets in metadata. The differences blossom from there.

In a hybrid application you run both versions of Angular at the same time.
That means that you need at least one module each from both AngularJS and Angular.
You will import `UpgradeModule` inside the NgModule, and then use it for
bootstrapping the AngularJS module.

<div class="alert is-helpful">

For more information, see [NgModules](guide/ngmodules).

</div>

### Bootstrapping hybrid applications

To bootstrap a hybrid application, you must bootstrap each of the Angular and
AngularJS parts of the application. You must bootstrap the Angular bits first and
then ask the `UpgradeModule` to bootstrap the AngularJS bits next.

In an AngularJS application you have a root AngularJS module, which will also
be used to bootstrap the AngularJS application.

<code-example path="upgrade-module/src/app/ajs-bootstrap/app.module.ts" region="ng1module" header="app.module.ts">
</code-example>

Pure AngularJS applications can be automatically bootstrapped by using an `ng-app`
directive somewhere on the HTML page. But for hybrid applications, you manually bootstrap via the
`UpgradeModule`. Therefore, it is a good preliminary step to switch AngularJS applications to use the
manual JavaScript [`angular.bootstrap`](https://docs.angularjs.org/api/ng/function/angular.bootstrap)
method even before switching them to hybrid mode.

Say you have an `ng-app` driven bootstrap such as this one:

<code-example path="upgrade-module/src/index-ng-app.html">
</code-example>

You can remove the `ng-app` and `ng-strict-di` directives from the HTML
and instead switch to calling `angular.bootstrap` from JavaScript, which
will result in the same thing:

<code-example path="upgrade-module/src/app/ajs-bootstrap/app.module.ts" region="bootstrap" header="app.module.ts">
</code-example>

To begin converting your AngularJS application to a hybrid, you need to load the Angular framework.
You can see how this can be done with SystemJS by following the instructions in [Setup](guide/setup),
selectively copying code from the [QuickStart github repository](https://github.com/angular/quickstart).

You also need to install the `@angular/upgrade` package via `npm install @angular/upgrade --save`
and add a mapping for the `@angular/upgrade/static` package:

<code-example path="upgrade-module/src/systemjs.config.1.js" region="upgrade-static-umd" header="systemjs.config.js (map)">
</code-example>

Next, create an `app.module.ts` file and add the following `NgModule` class:

<code-example path="upgrade-module/src/app/ajs-a-hybrid-bootstrap/app.module.ts" region="ngmodule" header="app.module.ts">
</code-example>

This bare minimum `NgModule` imports `BrowserModule`, the module every Angular browser-based app must have.
It also imports `UpgradeModule` from `@angular/upgrade/static`, which exports providers that will be used
for upgrading and downgrading services and components.

In the constructor of the `AppModule`, use dependency injection to get a hold of the `UpgradeModule` instance,
and use it to bootstrap the AngularJS app in the `AppModule.ngDoBootstrap` method.
The `upgrade.bootstrap` method takes the exact same arguments as [angular.bootstrap](https://docs.angularjs.org/api/ng/function/angular.bootstrap):

<div class="alert is-helpful">

Note that you do not add a `bootstrap` declaration to the `@NgModule` decorator, since
AngularJS will own the root template of the application.

</div>

Now you can bootstrap `AppModule` using the `platformBrowserDynamic.bootstrapModule` method.

<code-example path="upgrade-module/src/app/ajs-a-hybrid-bootstrap/app.module.ts" region="bootstrap" header="app.module.ts'">
</code-example>

Congratulations! You're running a hybrid application! The
existing AngularJS code works as before _and_ you're ready to start adding Angular code.

### Using Angular Components from AngularJS Code

<img src="generated/images/guide/upgrade/ajs-to-a.png" alt="Using an Angular component from AngularJS code" class="left">

Once you're running a hybrid app, you can start the gradual process of upgrading
code. One of the more common patterns for doing that is to use an Angular component
in an AngularJS context. This could be a completely new component or one that was
previously AngularJS but has been rewritten for Angular.

Say you have a simple Angular component that shows information about a hero:

<code-example path="upgrade-module/src/app/downgrade-static/hero-detail.component.ts" header="hero-detail.component.ts">
</code-example>

If you want to use this component from AngularJS, you need to *downgrade* it
using the `downgradeComponent()` method. The result is an AngularJS
*directive*, which you can then register in the AngularJS module:

<code-example path="upgrade-module/src/app/downgrade-static/app.module.ts" region="downgradecomponent" header="app.module.ts">
</code-example>

Because `HeroDetailComponent` is an Angular component, you must also add it to the
`declarations` in the `AppModule`.

And because this component is being used from the AngularJS module, and is an entry point into
the Angular application, you must add it to the `entryComponents` for the
NgModule.

<code-example path="upgrade-module/src/app/downgrade-static/app.module.ts" region="ngmodule" header="app.module.ts">
</code-example>

<div class="alert is-helpful">

All Angular components, directives and pipes must be declared in an NgModule.

</div>

The net result is an AngularJS directive called `heroDetail`, that you can
use like any other directive in AngularJS templates.

<code-example path="upgrade-module/src/index-downgrade-static.html" region="usecomponent">
</code-example>

<div class="alert is-helpful">

Note that this AngularJS is an element directive (`restrict: 'E'`) called `heroDetail`.
An AngularJS element directive is matched based on its _name_.
*The `selector` metadata of the downgraded Angular component is ignored.*

</div>

Most components are not quite this simple, of course. Many of them
have *inputs and outputs* that connect them to the outside world. An
Angular hero detail component with inputs and outputs might look
like this:

<code-example path="upgrade-module/src/app/downgrade-io/hero-detail.component.ts" header="hero-detail.component.ts">
</code-example>

These inputs and outputs can be supplied from the AngularJS template, and the
`downgradeComponent()` method takes care of wiring them up:

<code-example path="upgrade-module/src/index-downgrade-io.html" region="usecomponent">
</code-example>

Note that even though you are in an AngularJS template, **you're using Angular
attribute syntax to bind the inputs and outputs**. This is a requirement for downgraded
components. The expressions themselves are still regular AngularJS expressions.

<div class="callout is-important">

<header>
  Use kebab-case for downgraded component attributes
</header>

There's one notable exception to the rule of using Angular attribute syntax
for downgraded components. It has to do with input or output names that consist
of multiple words. In Angular, you would bind these attributes using camelCase:

<code-example format="">
  [myHero]="hero"
</code-example>

But when using them from AngularJS templates, you must use kebab-case:

<code-example format="">
  [my-hero]="hero"
</code-example>

</div>

The `$event` variable can be used in outputs to gain access to the
object that was emitted. In this case it will be the `Hero` object, because
that is what was passed to `this.deleted.emit()`.

Since this is an AngularJS template, you can still use other AngularJS
directives on the element, even though it has Angular binding attributes on it.
For example, you can easily make multiple copies of the component using `ng-repeat`:

<code-example path="upgrade-module/src/index-downgrade-io.html" region="userepeatedcomponent">
</code-example>

### Using AngularJS Component Directives from Angular Code

<img src="generated/images/guide/upgrade/a-to-ajs.png" alt="Using an AngularJS component from Angular code" class="left">

So, you can write an Angular component and then use it from AngularJS
code. This is useful when you start to migrate from lower-level
components and work your way up. But in some cases it is more convenient
to do things in the opposite order: To start with higher-level components
and work your way down. This too can be done using the `upgrade/static`.
You can *upgrade* AngularJS component directives and then use them from
Angular.

Not all kinds of AngularJS directives can be upgraded. The directive
really has to be a *component directive*, with the characteristics
[described in the preparation guide above](guide/upgrade#using-component-directives).
The safest bet for ensuring compatibility is using the
[component API](https://docs.angularjs.org/api/ng/type/angular.Module)
introduced in AngularJS 1.5.

A simple example of an upgradable component is one that just has a template
and a controller:

<code-example path="upgrade-module/src/app/upgrade-static/hero-detail.component.ts" region="hero-detail" header="hero-detail.component.ts">
</code-example>

You can *upgrade* this component to Angular using the `UpgradeComponent` class.
By creating a new Angular **directive** that extends `UpgradeComponent` and doing a `super` call
inside its constructor, you have a fully upgraded AngularJS component to be used inside Angular.
All that is left is to add it to `AppModule`'s `declarations` array.

<code-example path="upgrade-module/src/app/upgrade-static/hero-detail.component.ts" region="hero-detail-upgrade" header="hero-detail.component.ts">
</code-example>

<code-example path="upgrade-module/src/app/upgrade-static/app.module.ts" region="hero-detail-upgrade" header="app.module.ts">
</code-example>

<div class="alert is-helpful">

Upgraded components are Angular **directives**, instead of **components**, because Angular
is unaware that AngularJS will create elements under it. As far as Angular knows, the upgraded
component is just a directive - a tag - and Angular doesn't have to concern itself with
its children.

</div>

An upgraded component may also have inputs and outputs, as defined by
the scope/controller bindings of the original AngularJS component
directive. When you use the component from an Angular template,
provide the inputs and outputs using **Angular template syntax**,
observing the following rules:

<table>
  <tr>
    <th>
    </th>
    <th>
      Binding definition
    </th>
    <th>
      Template syntax
    </th>
  </tr>
  <tr>
    <th>
      Attribute binding
    </th>
    <td>

      `myAttribute: '@myAttribute'`

    </td>

    <td>

      `<my-component myAttribute="value">`

    </td>
  </tr>
  <tr>
    <th>
      Expression binding
    </th>
    <td>

      `myOutput: '&myOutput'`

    </td>
    <td>

      `<my-component (myOutput)="action()">`

    </td>
  </tr>
  <tr>
    <th>
      One-way binding
    </th>
    <td>

      `myValue: '<myValue'`

    </td>
    <td>

      `<my-component [myValue]="anExpression">`

    </td>
  </tr>
  <tr>
    <th>
      Two-way binding
    </th>
    <td>

      `myValue: '=myValue'`

    </td>
    <td>

      As a two-way binding: `<my-component [(myValue)]="anExpression">`.
      Since most AngularJS two-way bindings actually only need a one-way binding
      in practice, `<my-component [myValue]="anExpression">` is often enough.

    </td>
  </tr>
</table>

For example, imagine a hero detail AngularJS component directive
with one input and one output:

<code-example path="upgrade-module/src/app/upgrade-io/hero-detail.component.ts" region="hero-detail-io" header="hero-detail.component.ts">
</code-example>

You can upgrade this component to Angular, annotate inputs and outputs in the upgrade directive,
and then provide the input and output using Angular template syntax:

<code-example path="upgrade-module/src/app/upgrade-io/hero-detail.component.ts" region="hero-detail-io-upgrade" header="hero-detail.component.ts">
</code-example>

<code-example path="upgrade-module/src/app/upgrade-io/container.component.ts" header="container.component.ts">
</code-example>

### Projecting AngularJS Content into Angular Components

<img src="generated/images/guide/upgrade/ajs-to-a-with-projection.png" alt="Projecting AngularJS content into Angular" class="left">

When you are using a downgraded Angular component from an AngularJS
template, the need may arise to *transclude* some content into it. This
is also possible. While there is no such thing as transclusion in Angular,
there is a very similar concept called *content projection*. `upgrade/static`
is able to make these two features interoperate.

Angular components that support content projection make use of an `<ng-content>`
tag within them. Here's an example of such a component:

<code-example path="upgrade-module/src/app/ajs-to-a-projection/hero-detail.component.ts" header="hero-detail.component.ts">
</code-example>

When using the component from AngularJS, you can supply contents for it. Just
like they would be transcluded in AngularJS, they get projected to the location
of the `<ng-content>` tag in Angular:

<code-example path="upgrade-module/src/index-ajs-to-a-projection.html" region="usecomponent">
</code-example>

<div class="alert is-helpful">

When AngularJS content gets projected inside an Angular component, it still
remains in "AngularJS land" and is managed by the AngularJS framework.

</div>

### Transcluding Angular Content into AngularJS Component Directives

<img src="generated/images/guide/upgrade/a-to-ajs-with-transclusion.png" alt="Projecting Angular content into AngularJS" class="left">

Just as you can project AngularJS content into Angular components,
you can *transclude* Angular content into AngularJS components, whenever
you are using upgraded versions from them.

When an AngularJS component directive supports transclusion, it may use
the `ng-transclude` directive in its template to mark the transclusion
point:

<code-example path="upgrade-module/src/app/a-to-ajs-transclusion/hero-detail.component.ts" header="hero-detail.component.ts">
</code-example>

If you upgrade this component and use it from Angular, you can populate
the component tag with contents that will then get transcluded:

<code-example path="upgrade-module/src/app/a-to-ajs-transclusion/container.component.ts" header="container.component.ts">
</code-example>

### Making AngularJS Dependencies Injectable to Angular

When running a hybrid app, you may encounter situations where you need to inject
some AngularJS dependencies into your Angular code.
Maybe you have some business logic still in AngularJS services.
Maybe you want access to AngularJS's built-in services like `$location` or `$timeout`.

In these situations, it is possible to *upgrade* an AngularJS provider to
Angular. This makes it possible to then inject it somewhere in Angular
code. For example, you might have a service called `HeroesService` in AngularJS:

<code-example path="upgrade-module/src/app/ajs-to-a-providers/heroes.service.ts" header="heroes.service.ts">
</code-example>

You can upgrade the service using a Angular [factory provider](guide/dependency-injection-providers#factory-providers)
that requests the service from the AngularJS `$injector`.

Many developers prefer to declare the factory provider in a separate `ajs-upgraded-providers.ts` file
so that they are all together, making it easier to reference them, create new ones and
delete them once the upgrade is over.

It's also recommended to export the `heroesServiceFactory` function so that Ahead-of-Time
compilation can pick it up.

<div class="alert is-helpful">

**Note:** The 'heroes' string inside the factory refers to the AngularJS `HeroesService`.
It is common in AngularJS apps to choose a service name for the token, for example "heroes",
and append the "Service" suffix to create the class name.

</div>

<code-example path="upgrade-module/src/app/ajs-to-a-providers/ajs-upgraded-providers.ts" header="ajs-upgraded-providers.ts">
</code-example>

You can then provide the service to Angular by adding it to the `@NgModule`:

<code-example path="upgrade-module/src/app/ajs-to-a-providers/app.module.ts" region="register" header="app.module.ts">
</code-example>

Then use the service inside your component by injecting it in the component constructor using its class as a type annotation:

<code-example path="upgrade-module/src/app/ajs-to-a-providers/hero-detail.component.ts" header="hero-detail.component.ts">
</code-example>

<div class="alert is-helpful">

In this example you upgraded a service class.
You can use a TypeScript type annotation when you inject it. While it doesn't
affect how the dependency is handled, it enables the benefits of static type
checking. This is not required though, and any AngularJS service, factory, or
provider can be upgraded.

</div>

### Making Angular Dependencies Injectable to AngularJS

In addition to upgrading AngularJS dependencies, you can also *downgrade*
Angular dependencies, so that you can use them from AngularJS. This can be
useful when you start migrating services to Angular or creating new services
in Angular while retaining components written in AngularJS.

For example, you might have an Angular service called `Heroes`:

<code-example path="upgrade-module/src/app/a-to-ajs-providers/heroes.ts" header="heroes.ts">
</code-example>

Again, as with Angular components, register the provider with the `NgModule` by adding it to the module's `providers` list.

<code-example path="upgrade-module/src/app/a-to-ajs-providers/app.module.ts" region="ngmodule" header="app.module.ts">
</code-example>

Now wrap the Angular `Heroes` in an *AngularJS factory function* using `downgradeInjectable()`
and plug the factory into an AngularJS module.
The name of the AngularJS dependency is up to you:

<code-example path="upgrade-module/src/app/a-to-ajs-providers/app.module.ts" region="register" header="app.module.ts">
</code-example>

After this, the service is injectable anywhere in AngularJS code:

<code-example path="upgrade-module/src/app/a-to-ajs-providers/hero-detail.component.ts" header="hero-detail.component.ts">
</code-example>

## Using Ahead-of-time compilation with hybrid apps

You can take advantage of Ahead-of-time (AOT) compilation on hybrid apps just like on any other
Angular application.
The setup for an hybrid app is mostly the same as described in
[the Ahead-of-time Compilation chapter](guide/aot-compiler)
save for differences in `index.html` and `main-aot.ts`

The `index.html` will likely have script tags loading AngularJS files, so the `index.html`
for AOT must also load those files.
An easy way to copy them is by adding each to the `copy-dist-files.js` file.

You'll need to use the generated `AppModuleFactory`, instead of the original `AppModule` to
bootstrap the hybrid app:

<code-example path="upgrade-phonecat-2-hybrid/app/main-aot.ts" header="app/main-aot.ts">
</code-example>

And that's all you need do to get the full benefit of AOT for Angular apps!

## PhoneCat Upgrade Tutorial

In this section, you'll learn to prepare and upgrade an application with `ngUpgrade`.
The example app is [Angular PhoneCat](https://github.com/angular/angular-phonecat)
from [the original AngularJS tutorial](https://docs.angularjs.org/tutorial),
which is where many of us began our Angular adventures. Now you'll see how to
bring that application to the brave new world of Angular.

During the process you'll learn how to apply the steps outlined in the
[preparation guide](guide/upgrade#preparation). You'll align the application
with Angular and also start writing in TypeScript.

To follow along with the tutorial, clone the
[angular-phonecat](https://github.com/angular/angular-phonecat) repository
and apply the steps as you go.

In terms of project structure, this is where the work begins:

<div class='filetree'>
  <div class='file'>
    angular-phonecat
  </div>
  <div class='children'>
    <div class='file'>
      bower.json
    </div>
    <div class='file'>
      karma.conf.js
    </div>
    <div class='file'>
      package.json
    </div>
    <div class='file'>
      app
    </div>
    <div class='children'>
      <div class='file'>
        core
      </div>
      <div class='children'>
        <div class='file'>
          checkmark
        </div>
        <div class='children'>
          <div class='file'>
            checkmark.filter.js
          </div>
          <div class='file'>
            checkmark.filter.spec.js
          </div>
        </div>
        <div class='file'>
          phone
        </div>
        <div class='children'>
          <div class='file'>
            phone.module.js
          </div>
          <div class='file'>
            phone.service.js
          </div>
          <div class='file'>
            phone.service.spec.js
          </div>
        </div>
        <div class='file'>
          core.module.js
        </div>
      </div>
      <div class='file'>
        phone-detail
      </div>
      <div class='children'>
        <div class='file'>
          phone-detail.component.js
        </div>
        <div class='file'>
          phone-detail.component.spec.js
        </div>
        <div class='file'>
          phone-detail.module.js
        </div>
        <div class='file'>
          phone-detail.template.html
        </div>
      </div>
      <div class='file'>
        phone-list
      </div>
      <div class='children'>
        <div class='file'>
          phone-list.component.js
        </div>
        <div class='file'>
          phone-list.component.spec.js
        </div>
        <div class='file'>
          phone-list.module.js
        </div>
        <div class='file'>
          phone-list.template.html
        </div>
      </div>
      <div class='file'>
        img
      </div>
      <div class='children'>
        <div class='file'>
           ...
        </div>
      </div>
      <div class='file'>
        phones
      </div>
      <div class='children'>
        <div class='file'>
           ...
        </div>
      </div>
      <div class='file'>
        app.animations.js
      </div>
      <div class='file'>
        app.config.js
      </div>
      <div class='file'>
        app.css
      </div>
      <div class='file'>
        app.module.js
      </div>
      <div class='file'>
        index.html
      </div>
    </div>
    <div class='file'>
      e2e-tests
    </div>
    <div class='children'>
      <div class='file'>
        protractor-conf.js
      </div>
      <div class='file'>
        scenarios.js
      </div>
    </div>
  </div>
</div>

This is actually a pretty good starting point. The code uses the AngularJS 1.5
component API and the organization follows the
[AngularJS Style Guide](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md),
which is an important [preparation step](guide/upgrade#follow-the-angular-styleguide) before
a successful upgrade.

* Each component, service, and filter is in its own source file, as per the
  [Rule of 1](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#single-responsibility).

* The `core`, `phone-detail`, and `phone-list` modules are each in their
  own subdirectory. Those subdirectories contain the JavaScript code as well as
  the HTML templates that go with each particular feature. This is in line with the
  [Folders-by-Feature Structure](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#folders-by-feature-structure)
  and [Modularity](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#modularity)
  rules.

* Unit tests are located side-by-side with application code where they are easily
  found, as described in the rules for
  [Organizing Tests](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#organizing-tests).

### Switching to TypeScript

Since you're going to be writing Angular code in TypeScript, it makes sense to
bring in the TypeScript compiler even before you begin upgrading.

You'll also start to gradually phase out the Bower package manager in favor
of NPM, installing all new dependencies using NPM, and eventually removing Bower from the project.

Begin by installing TypeScript to the project.

<code-example format="">
  npm i typescript --save-dev
</code-example>

Install type definitions for the existing libraries that
you're using but that don't come with prepackaged types: AngularJS and the
Jasmine unit test framework.

<code-example format="">
  npm install @types/jasmine @types/angular @types/angular-animate @types/angular-cookies @types/angular-mocks @types/angular-resource @types/angular-route @types/angular-sanitize --save-dev
</code-example>

You should also configure the TypeScript compiler with a `tsconfig.json` in the project directory
as described in the [TypeScript Configuration](guide/typescript-configuration) guide.
The `tsconfig.json` file tells the TypeScript compiler how to turn your TypeScript files
into ES5 code bundled into CommonJS modules.

Finally, you should add some npm scripts in `package.json` to compile the TypeScript files to
JavaScript (based on the `tsconfig.json` configuration file):

<code-example format="">
  "script": {
    "tsc": "tsc",
    "tsc:w": "tsc -w",
    ...
</code-example>

Now launch the TypeScript compiler from the command line in watch mode:

<code-example format="">
  npm run tsc:w
</code-example>

Keep this process running in the background, watching and recompiling as you make changes.

Next, convert your current JavaScript files into TypeScript. Since
TypeScript is a super-set of ECMAScript 2015, which in turn is a super-set
of ECMAScript 5, you can simply switch the file extensions from `.js` to `.ts`
and everything will work just like it did before. As the TypeScript compiler
runs, it emits the corresponding `.js` file for every `.ts` file and the
compiled JavaScript is what actually gets executed. If you start
the project HTTP server with `npm start`, you should see the fully functional
application in your browser.

Now that you have TypeScript though, you can start benefiting from some of its
features. There's a lot of value the language can provide to AngularJS applications.

For one thing, TypeScript is a superset of ES2015. Any app that has previously
been written in ES5 - like the PhoneCat example has - can with TypeScript
start incorporating all of the JavaScript features that are new to ES2015.
These include things like `let`s and `const`s, arrow functions, default function
parameters, and destructuring assignments.

Another thing you can do is start adding *type safety* to your code. This has
actually partially already happened because of the AngularJS typings you installed.
TypeScript are checking that you are calling AngularJS APIs correctly when you do
things like register components to Angular modules.

But you can also start adding *type annotations* to get even more
out of TypeScript's type system. For instance, you can annotate the checkmark
filter so that it explicitly expects booleans as arguments. This makes it clearer
what the filter is supposed to do.

<code-example path="upgrade-phonecat-1-typescript/app/core/checkmark/checkmark.filter.ts" header="app/core/checkmark/checkmark.filter.ts">
</code-example>

In the `Phone` service, you can explicitly annotate the `$resource` service dependency
as an `angular.resource.IResourceService` - a type defined by the AngularJS typings.

<code-example path="upgrade-phonecat-1-typescript/app/core/phone/phone.service.ts" header="app/core/phone/phone.service.ts">
</code-example>

You can apply the same trick to the application's route configuration file in `app.config.ts`,
where you are using the location and route services. By annotating them accordingly TypeScript
can verify you're calling their APIs with the correct kinds of arguments.

<code-example path="upgrade-phonecat-1-typescript/app/app.config.ts" header="app/app.config.ts">
</code-example>

<div class="alert is-helpful">

The [AngularJS 1.x type definitions](https://www.npmjs.com/package/@types/angular)
you installed are not officially maintained by the Angular team,
but are quite comprehensive. It is possible to make an AngularJS 1.x application
fully type-annotated with the help of these definitions.

If this is something you wanted to do, it would be a good idea to enable
the `noImplicitAny` configuration option in `tsconfig.json`. This would
cause the TypeScript compiler to display a warning when there's any code that
does not yet have type annotations. You could use it as a guide to inform
us about how close you are to having a fully annotated project.

</div>

Another TypeScript feature you can make use of is *classes*. In particular, you
can turn component controllers into classes. That way they'll be a step
closer to becoming Angular component classes, which will make life
easier once you upgrade.

AngularJS expects controllers to be constructor functions. That's exactly what
ES2015/TypeScript classes are under the hood, so that means you can just plug in a
class as a component controller and AngularJS will happily use it.

Here's what the new class for the phone list component controller looks like:

<code-example path="upgrade-phonecat-1-typescript/app/phone-list/phone-list.component.ts" header="app/phone-list/phone-list.component.ts">
</code-example>

What was previously done in the controller function is now done in the class
constructor function. The dependency injection annotations are attached
to the class using a static property `$inject`. At runtime this becomes the
`PhoneListController.$inject` property.

The class additionally declares three members: The array of phones, the name of
the current sort key, and the search query. These are all things you have already
been attaching to the controller but that weren't explicitly declared anywhere.
The last one of these isn't actually used in the TypeScript code since it's only
referred to in the template, but for the sake of clarity you should define all of the
controller members.

In the Phone detail controller, you'll have two members: One for the phone
that the user is looking at and another for the URL of the currently displayed image:

<code-example path="upgrade-phonecat-1-typescript/app/phone-detail/phone-detail.component.ts" header="app/phone-detail/phone-detail.component.ts">
</code-example>

This makes the controller code look a lot more like Angular already. You're
all set to actually introduce Angular into the project.

If you had any AngularJS services in the project, those would also be
a good candidate for converting to classes, since like controllers,
they're also constructor functions. But you only have the `Phone` factory
in this project, and that's a bit special since it's an `ngResource`
factory. So you won't be doing anything to it in the preparation stage.
You'll instead turn it directly into an Angular service.

### Installing Angular

Having completed the preparation work, get going with the Angular
upgrade of PhoneCat. You'll do this incrementally with the help of
[ngUpgrade](#upgrading-with-ngupgrade) that comes with Angular.
By the time you're done, you'll be able to remove AngularJS from the project
completely, but the key is to do this piece by piece without breaking the application.

<div class="alert is-important">

The project also contains some animations.
You won't upgrade them in this version of the guide.
Turn to the [Angular animations](guide/animations) guide to learn about that.

</div>

Install Angular into the project, along with the SystemJS module loader.
Take a look at the results of the [Setup](guide/setup) instructions
and get the following configurations from there:

* Add Angular and the other new dependencies to `package.json`
* The SystemJS configuration file `systemjs.config.js` to the project root directory.

Once these are done, run:

<code-example format="">
  npm install
</code-example>

Soon you can load Angular dependencies into the application via `index.html`,
but first you need to do some directory path adjustments.
You'll need to load files from `node_modules` and the project root instead of
from the `/app` directory as you've been doing to this point.

Move the `app/index.html` file to the project root directory. Then change the
development server root path in `package.json` to also point to the project root
instead of `app`:

<code-example format="">
  "start": "http-server ./ -a localhost -p 8000 -c-1",
</code-example>

Now you're able to serve everything from the project root to the web browser. But you do *not*
want to have to change all the image and data paths used in the application code to match
the development setup. For that reason, you'll add a `<base>` tag to `index.html`, which will
cause relative URLs to be resolved back to the `/app` directory:

<code-example path="upgrade-phonecat-2-hybrid/index.html" region="base" header="index.html">
</code-example>

Now you can load Angular via SystemJS. You'll add the Angular polyfills and the
SystemJS config to the end of the `<head>` section, and then you'll use `System.import`
to load the actual application:

<code-example path="upgrade-phonecat-2-hybrid/index.html" region="angular" header="index.html">
</code-example>

You also need to make a couple of adjustments
to the `systemjs.config.js` file installed during [setup](guide/setup).

Point the browser to the project root when loading things through SystemJS,
instead of using the  `<base>` URL.

Install the `upgrade` package via `npm install @angular/upgrade --save`
and add a mapping for the `@angular/upgrade/static` package.

<code-example path="upgrade-phonecat-2-hybrid/systemjs.config.1.js" region="paths" header="systemjs.config.js">
</code-example>

### Creating the _AppModule_

Now create the root `NgModule` class called `AppModule`.
There is already a file named `app.module.ts` that holds the AngularJS module.
Rename it to `app.module.ajs.ts` and update the corresponding script name in the `index.html` as well.
The file contents remain:

<code-example path="upgrade-phonecat-2-hybrid/app/app.module.ajs.ts" header="app.module.ajs.ts">
</code-example>

Now create a new `app.module.ts` with the minimum `NgModule` class:

<code-example path="upgrade-phonecat-2-hybrid/app/app.module.ts" region="bare" header="app.module.ts">
</code-example>

### Bootstrapping a hybrid PhoneCat

Next, you'll bootstrap the application as a *hybrid application*
that supports both AngularJS and Angular components. After that,
you can start converting the individual pieces to Angular.

The application is currently bootstrapped using the AngularJS `ng-app` directive
attached to the `<html>` element of the host page. This will no longer work in the hybrid
app. Switch to the [ngUpgrade bootstrap](#bootstrapping-hybrid-applications) method
instead.

First, remove the `ng-app` attribute from `index.html`.
Then import `UpgradeModule` in the `AppModule`, and override its `ngDoBootstrap` method:

<code-example path="upgrade-phonecat-2-hybrid/app/app.module.ts" region="upgrademodule" header="app/app.module.ts">
</code-example>

Note that you are bootstrapping the AngularJS module from inside `ngDoBootstrap`.
The arguments are the same as you would pass to `angular.bootstrap` if you were manually
bootstrapping AngularJS: the root element of the application; and an array of the
AngularJS 1.x modules that you want to load.

Finally, bootstrap the `AppModule` in `app/main.ts`.
This file has been configured as the application entrypoint in `systemjs.config.js`,
so it is already being loaded by the browser.

<code-example path="upgrade-phonecat-2-hybrid/app/main.ts" region="bootstrap" header="app/main.ts">
</code-example>

Now you're running both AngularJS and Angular at the same time. That's pretty
exciting! You're not running any actual Angular components yet. That's next.

<div class="alert is-helpful">

#### Why declare _angular_ as _angular.IAngularStatic_?

`@types/angular` is declared as a UMD module, and due to the way
<a href="https://github.com/Microsoft/TypeScript/wiki/What's-new-in-TypeScript#support-for-umd-module-definitions">UMD typings</a>
work, once you have an ES6 `import` statement in a file all UMD typed modules must also be
imported via `import` statements instead of being globally available.

AngularJS is currently loaded by a script tag in `index.html`, which means that the whole app
has access to it as a global and uses the same instance of the `angular` variable.
If you used `import * as angular from 'angular'` instead, you'd also have to
load every file in the AngularJS app to use ES2015 modules in order to ensure AngularJS was being
loaded correctly.

This is a considerable effort and it often isn't worth it, especially since you are in the
process of moving your code to Angular.
Instead, declare `angular` as `angular.IAngularStatic` to indicate it is a global variable
and still have full typing support.

</div>

### Upgrading the Phone service

The first piece you'll port over to Angular is the `Phone` service, which
resides in `app/core/phone/phone.service.ts` and makes it possible for components
to load phone information from the server. Right now it's implemented with
ngResource and you're using it for two things:

* For loading the list of all phones into the phone list component.
* For loading the details of a single phone into the phone detail component.

You can replace this implementation with an Angular service class, while
keeping the controllers in AngularJS land.

In the new version, you import the Angular HTTP module and call its `HttpClient` service instead of `ngResource`.

Re-open the `app.module.ts` file, import and add `HttpClientModule` to the `imports` array of the `AppModule`:

<code-example path="upgrade-phonecat-2-hybrid/app/app.module.ts" region="httpclientmodule" header="app.module.ts">
</code-example>

Now you're ready to upgrade the Phone service itself. Replace the ngResource-based
service in `phone.service.ts` with a TypeScript class decorated as `@Injectable`:

<code-example path="upgrade-phonecat-2-hybrid/app/core/phone/phone.service.ts" region="classdef" header="app/core/phone/phone.service.ts (skeleton)" linenums="false">
</code-example>

The `@Injectable` decorator will attach some dependency injection metadata
to the class, letting Angular know about its dependencies. As described
by the [Dependency Injection Guide](guide/dependency-injection),
this is a marker decorator you need to use for classes that have no other
Angular decorators but still need to have their dependencies injected.

In its constructor the class expects to get the `HttpClient` service. It will
be injected to it and it is stored as a private field. The service is then
used in the two instance methods, one of which loads the list of all phones,
and the other loads the details of a specified phone:

<code-example path="upgrade-phonecat-2-hybrid/app/core/phone/phone.service.ts" region="fullclass" header="app/core/phone/phone.service.ts">
</code-example>

The methods now return observables of type `PhoneData` and `PhoneData[]`. This is
a type you don't have yet. Add a simple interface for it:

<code-example path="upgrade-phonecat-2-hybrid/app/core/phone/phone.service.ts" region="phonedata-interface" header="app/core/phone/phone.service.ts (interface)" linenums="false">
</code-example>

`@angular/upgrade/static` has a `downgradeInjectable` method for the purpose of making
Angular services available to AngularJS code. Use it to plug in the `Phone` service:

<code-example path="upgrade-phonecat-2-hybrid/app/core/phone/phone.service.ts" region="downgrade-injectable" header="app/core/phone/phone.service.ts (downgrade)" linenums="false">
</code-example>

Here's the full, final code for the service:

<code-example path="upgrade-phonecat-2-hybrid/app/core/phone/phone.service.ts" header="app/core/phone/phone.service.ts">
</code-example>

Notice that you're importing the `map` operator of the RxJS `Observable` separately.
Do this for every RxJS operator.

The new `Phone` service has the same features as the original, `ngResource`-based service.
Because it's an Angular service, you register it with the `NgModule` providers:

<code-example path="upgrade-phonecat-2-hybrid/app/app.module.ts" region="phone" header="app.module.ts">
</code-example>

Now that you are loading `phone.service.ts` through an import that is resolved
by SystemJS, you should **remove the &lt;script&gt; tag** for the service from `index.html`.
This is something you'll do to all components as you upgrade them. Simultaneously
with the AngularJS to Angular upgrade you're also migrating code from scripts to modules.

At this point, you can switch the two components to use the new service
instead of the old one.  While you `$inject` it as the downgraded `phone` factory,
it's really an instance of the `Phone` class and you annotate its type accordingly:

<code-example path="upgrade-phonecat-2-hybrid/app/phone-list/phone-list.component.ajs.ts" header="app/phone-list/phone-list.component.ts">
</code-example>

<code-example path="upgrade-phonecat-2-hybrid/app/phone-detail/phone-detail.component.ajs.ts" header="app/phone-detail/phone-detail.component.ts">
</code-example>

Now there are two AngularJS components using an Angular service!
The components don't need to be aware of this, though the fact that the
service returns observables and not promises is a bit of a giveaway.
In any case, what you've achieved is a migration of a service to Angular
without having to yet migrate the components that use it.

<div class="alert is-helpful">

You could use the `toPromise` method of `Observable` to turn those
observables into promises in the service. In many cases that reduce
the number of changes to the component controllers.

</div>

### Upgrading Components

Upgrade the AngularJS components to Angular components next.
Do it one component at a time while still keeping the application in hybrid mode.
As you make these conversions, you'll also define your first Angular *pipes*.

Look at the phone list component first. Right now it contains a TypeScript
controller class and a component definition object. You can morph this into
an Angular component by just renaming the controller class and turning the
AngularJS component definition object into an Angular `@Component` decorator.
You can then also remove the static `$inject` property from the class:

<code-example path="upgrade-phonecat-2-hybrid/app/phone-list/phone-list.component.ts" region="initialclass" header="app/phone-list/phone-list.component.ts">
</code-example>

The `selector` attribute is a CSS selector that defines where on the page the component
should go. In AngularJS you do matching based on component names, but in Angular you
have these explicit selectors. This one will match elements with the name `phone-list`,
just like the AngularJS version did.

Now convert the template of this component into Angular syntax.
The search controls replace the AngularJS `$ctrl` expressions
with Angular's two-way `[(ngModel)]` binding syntax:

<code-example path="upgrade-phonecat-2-hybrid/app/phone-list/phone-list.template.html" region="controls" header="app/phone-list/phone-list.template.html (search controls)" linenums="false">
</code-example>

Replace the list's `ng-repeat` with an `*ngFor` as
[described in the Template Syntax page](guide/template-syntax#directives).
Replace the image tag's `ng-src` with a binding to the native `src` property.

<code-example path="upgrade-phonecat-2-hybrid/app/phone-list/phone-list.template.html" region="list" header="app/phone-list/phone-list.template.html (phones)" linenums="false">
</code-example>

#### No Angular _filter_ or _orderBy_ filters

The built-in AngularJS `filter` and `orderBy` filters do not exist in Angular,
so you need to do the filtering and sorting yourself.

You replaced the `filter` and `orderBy` filters with bindings to the `getPhones()` controller method,
which implements the filtering and ordering logic inside the component itself.

<code-example path="upgrade-phonecat-2-hybrid/app/phone-list/phone-list.component.ts" region="getphones" header="app/phone-list/phone-list.component.ts">
</code-example>

Now you need to downgrade the Angular component so you can use it in AngularJS.
Instead of registering a component, you register a `phoneList` *directive*,
a downgraded version of the Angular component.

The `as angular.IDirectiveFactory` cast tells the TypeScript compiler
that the return value of the `downgradeComponent` method is a directive factory.

<code-example path="upgrade-phonecat-2-hybrid/app/phone-list/phone-list.component.ts" region="downgrade-component" header="app/phone-list/phone-list.component.ts">
</code-example>

The new `PhoneListComponent` uses the Angular `ngModel` directive, located in the `FormsModule`.
Add the `FormsModule` to `NgModule` imports, declare the new `PhoneListComponent` and
finally add it to `entryComponents` since you downgraded it:

<code-example path="upgrade-phonecat-2-hybrid/app/app.module.ts" region="phonelist" header="app.module.ts">
</code-example>

Remove the &lt;script&gt; tag for the phone list component from `index.html`.

Now set the remaining `phone-detail.component.ts` as follows:

<code-example path="upgrade-phonecat-2-hybrid/app/phone-detail/phone-detail.component.ts" header="app/phone-detail/phone-detail.component.ts">
</code-example>

This is similar to the phone list component.
The new wrinkle is the `RouteParams` type annotation that identifies the `routeParams` dependency.

The AngularJS injector has an AngularJS router dependency called `$routeParams`,
which was injected into `PhoneDetails` when it was still an AngularJS controller.
You intend to inject it into the new `PhoneDetailsComponent`.

Unfortunately, AngularJS dependencies are not automatically available to Angular components.
You must upgrade this service via a [factory provider](guide/upgrade#making-angularjs-dependencies-injectable-to-angular)
to make `$routeParams` an Angular injectable.
Do that in a new file called `ajs-upgraded-providers.ts` and import it in `app.module.ts`:

<code-example path="upgrade-phonecat-2-hybrid/app/ajs-upgraded-providers.ts" header="app/ajs-upgraded-providers.ts">
</code-example>

<code-example path="upgrade-phonecat-2-hybrid/app/app.module.ts" region="routeparams" header="app/app.module.ts ($routeParams)" linenums="false">
</code-example>

Convert the phone detail component template into Angular syntax as follows:

<code-example path="upgrade-phonecat-2-hybrid/app/phone-detail/phone-detail.template.html" header="app/phone-detail/phone-detail.template.html">
</code-example>

There are several notable changes here:

* You've removed the `$ctrl.` prefix from all expressions.

* You've replaced `ng-src` with property
  bindings for the standard `src` property.

* You're using the property binding syntax around `ng-class`. Though Angular
  does have [a very similar `ngClass`](guide/template-syntax#directives)
  as AngularJS does, its value is not magically evaluated as an expression.
  In Angular, you always specify  in the template when an attribute's value is
  a property expression, as opposed to a literal string.

* You've replaced `ng-repeat`s with `*ngFor`s.

* You've replaced `ng-click` with an event binding for the standard `click`.

* You've wrapped the whole template in an `ngIf` that causes it only to be
  rendered when there is a phone present. You need this because when the component
  first loads, you don't have `phone` yet and the expressions will refer to a
  non-existing value. Unlike in AngularJS, Angular expressions do not fail silently
  when you try to refer to properties on undefined objects. You need to be explicit
  about cases where this is expected.

Add `PhoneDetailComponent` component to the `NgModule` _declarations_ and _entryComponents_:

<code-example path="upgrade-phonecat-2-hybrid/app/app.module.ts" region="phonedetail" header="app.module.ts">
</code-example>

You should now also remove the phone detail component &lt;script&gt; tag from `index.html`.

#### Add the _CheckmarkPipe_

The AngularJS directive had a `checkmark` _filter_.
Turn that into an Angular **pipe**.

There is no upgrade method to convert filters into pipes.
You won't miss it.
It's easy to turn the filter function into an equivalent Pipe class.
The implementation is the same as before, repackaged in the `transform` method.
Rename the file to `checkmark.pipe.ts` to conform with Angular conventions:

<code-example path="upgrade-phonecat-2-hybrid/app/core/checkmark/checkmark.pipe.ts" header="app/core/checkmark/checkmark.pipe.ts" linenums="false">
</code-example>

Now import and declare the newly created pipe and
remove the filter &lt;script&gt; tag from `index.html`:

<code-example path="upgrade-phonecat-2-hybrid/app/app.module.ts" region="checkmarkpipe" header="app.module.ts">
</code-example>

### AOT compile the hybrid app

To use AOT with a hybrid app, you have to first set it up like any other Angular application,
as shown in [the Ahead-of-time Compilation chapter](guide/aot-compiler).

Then change `main-aot.ts` to bootstrap the `AppComponentFactory` that was generated
by the AOT compiler:

<code-example path="upgrade-phonecat-2-hybrid/app/main-aot.ts" header="app/main-aot.ts">
</code-example>

You need to load all the AngularJS files you already use in `index.html` in `aot/index.html`
as well:

<code-example path="upgrade-phonecat-2-hybrid/aot/index.html" header="aot/index.html">
</code-example>

These files need to be copied together with the polyfills. The files the application
needs at runtime, like the `.json` phone lists and images, also need to be copied.

Install `fs-extra` via `npm install fs-extra --save-dev` for better file copying, and change
`copy-dist-files.js` to the following:

<code-example path="upgrade-phonecat-2-hybrid/copy-dist-files.js" header="copy-dist-files.js">
</code-example>

And that's all you need to use AOT while upgrading your app!

### Adding The Angular Router And Bootstrap

At this point, you've replaced all AngularJS application components with
their Angular counterparts, even though you're still serving them from the AngularJS router.

#### Add the Angular router

Angular has an [all-new router](guide/router).

Like all routers, it needs a place in the UI to display routed views.
For Angular that's the `<router-outlet>` and it belongs in a *root component*
at the top of the applications component tree.

You don't yet have such a root component, because the app is still managed as an AngularJS app.
Create a new `app.component.ts` file with the following `AppComponent` class:

<code-example path="upgrade-phonecat-3-final/app/app.component.ts" header="app/app.component.ts">
</code-example>

It has a simple template that only includes the `<router-outlet>.
This component just renders the contents of the active route and nothing else.

The selector tells Angular to plug this root component into the `<phonecat-app>`
element on the host web page when the application launches.

Add this `<phonecat-app>` element to the `index.html`.
It replaces the old AngularJS `ng-view` directive:

<code-example path="upgrade-phonecat-3-final/index.html" region="appcomponent" header="index.html (body)" linenums="false">
</code-example>

#### Create the _Routing Module_
A router needs configuration whether it's the AngularJS or Angular or any other router.

The details of Angular router configuration are best left to the [Routing documentation](guide/router)
which recommends that you create a `NgModule` dedicated to router configuration
(called a _Routing Module_).

<code-example path="upgrade-phonecat-3-final/app/app-routing.module.ts" header="app/app-routing.module.ts">
</code-example>

This module defines a `routes` object with two routes to the two phone components
and a default route for the empty path.
It passes the `routes` to the `RouterModule.forRoot` method which does the rest.

A couple of extra providers enable routing with "hash" URLs such as `#!/phones`
instead of the default "push state" strategy.

Now update the `AppModule` to import this `AppRoutingModule` and also the
declare the root `AppComponent` as the bootstrap component.
That tells Angular that it should bootstrap the app with the _root_ `AppComponent` and
insert its view into the host web page.

You must also remove the bootstrap of the AngularJS module from `ngDoBootstrap()` in `app.module.ts`
and the `UpgradeModule` import.

<code-example path="upgrade-phonecat-3-final/app/app.module.ts" header="app/app.module.ts">
</code-example>

And since you are routing to `PhoneListComponent` and `PhoneDetailComponent` directly rather than
using a route template with a `<phone-list>` or `<phone-detail>` tag, you can do away with their
Angular selectors as well.

#### Generate links for each phone

You no longer have to hardcode the links to phone details in the phone list.
You can generate data bindings for each phone's `id` to the `routerLink` directive
and let that directive construct the appropriate URL to the `PhoneDetailComponent`:

<code-example path="upgrade-phonecat-3-final/app/phone-list/phone-list.template.html" region="list" header="app/phone-list/phone-list.template.html (list with links)" linenums="false">
</code-example>

<div class="alert is-helpful">

See the [Routing](guide/router) page for details.

</div><br>

#### Use route parameters

The Angular router passes route parameters differently.
Correct the `PhoneDetail` component constructor to expect an injected `ActivatedRoute` object.
Extract the `phoneId` from the `ActivatedRoute.snapshot.params` and fetch the phone data as before:

<code-example path="upgrade-phonecat-3-final/app/phone-detail/phone-detail.component.ts" header="app/phone-detail/phone-detail.component.ts">
</code-example>

You are now running a pure Angular application!

### Say Goodbye to AngularJS

It is time to take off the training wheels and let the application begin
its new life as a pure, shiny Angular app. The remaining tasks all have to
do with removing code - which of course is every programmer's favorite task!

The application is still bootstrapped as a hybrid app.
There's no need for that anymore.

Switch the bootstrap method of the application from the `UpgradeModule` to the Angular way.

<code-example path="upgrade-phonecat-3-final/app/main.ts" header="main.ts">
</code-example>

If you haven't already, remove all references to the `UpgradeModule` from `app.module.ts`,
as well as any [factory provider](guide/upgrade#making-angularjs-dependencies-injectable-to-angular)
for AngularJS services, and the `app/ajs-upgraded-providers.ts` file.

Also remove any `downgradeInjectable()` or `downgradeComponent()` you find,
together with the associated AngularJS factory or directive declarations.
Since you no longer have downgraded components, you no longer list them
in `entryComponents`.

<code-example path="upgrade-phonecat-3-final/app/app.module.ts" header="app.module.ts">
</code-example>

You may also completely remove the following files. They are AngularJS
module configuration files and not needed in Angular:

* `app/app.module.ajs.ts`
* `app/app.config.ts`
* `app/core/core.module.ts`
* `app/core/phone/phone.module.ts`
* `app/phone-detail/phone-detail.module.ts`
* `app/phone-list/phone-list.module.ts`

The external typings for AngularJS may be uninstalled as well. The only ones
you still need are for Jasmine and Angular polyfills.
The `@angular/upgrade` package and its mapping in `systemjs.config.js` can also go.

<code-example format="">
  npm uninstall @angular/upgrade --save
  npm uninstall @types/angular @types/angular-animate @types/angular-cookies @types/angular-mocks @types/angular-resource @types/angular-route @types/angular-sanitize --save-dev
</code-example>

Finally, from `index.html`, remove all references to AngularJS scripts and jQuery.
When you're done, this is what it should look like:

<code-example path="upgrade-phonecat-3-final/index.html" region="full" header="index.html">
</code-example>

That is the last you'll see of AngularJS! It has served us well but now
it's time to say goodbye.

## Appendix: Upgrading PhoneCat Tests

Tests can not only be retained through an upgrade process, but they can also be
used as a valuable safety measure when ensuring that the application does not
break during the upgrade. E2E tests are especially useful for this purpose.

### E2E Tests

The PhoneCat project has both E2E Protractor tests and some Karma unit tests in it.
Of these two, E2E tests can be dealt with much more easily: By definition,
E2E tests access the application from the *outside* by interacting with
the various UI elements the app puts on the screen. E2E tests aren't really that
concerned with the internal structure of the application components. That
also means that, although you modify the project quite a bit during the upgrade, the E2E
test suite should keep passing with just minor modifications. You
didn't change how the application behaves from the user's point of view.

During TypeScript conversion, there is nothing to do to keep E2E tests
working. But when you change the bootstrap to that of a Hybrid app,
you must make a few changes.

Update the `protractor-conf.js` to sync with hybrid apps:

<code-example format="">
  ng12Hybrid: true
</code-example>

When you start to upgrade components and their templates to Angular, you'll make more changes
because the E2E tests have matchers that are specific to AngularJS.
For PhoneCat you need to make the following changes in order to make things work with Angular:

<table>
  <tr>
    <th>
      Previous code
    </th>
    <th>
      New code
    </th>
    <th>
      Notes
    </th>
  </tr>
  <tr>
    <td>

      `by.repeater('phone in $ctrl.phones').column('phone.name')`

    </td>
    <td>

      `by.css('.phones .name')`

    </td>
    <td>

      The repeater matcher relies on AngularJS `ng-repeat`

    </td>
  </tr>
  <tr>
    <td>

      `by.repeater('phone in $ctrl.phones')`

    </td>
    <td>

      `by.css('.phones li')`

    </td>

    <td>

      The repeater matcher relies on AngularJS `ng-repeat`

    </td>
  </tr>
  <tr>
    <td>

      `by.model('$ctrl.query')`

    </td>
    <td>

      `by.css('input')`

    </td>
    <td>

      The model matcher relies on AngularJS `ng-model`

    </td>
  </tr>
  <tr>
    <td>

      `by.model('$ctrl.orderProp')`

    </td>
    <td>

      `by.css('select')`

    </td>
    <td>

      The model matcher relies on AngularJS `ng-model`

    </td>
  </tr>
  <tr>
    <td>

      `by.binding('$ctrl.phone.name')`

    </td>
    <td>

      `by.css('h1')`

    </td>
    <td>

      The binding matcher relies on AngularJS data binding

    </td>
  </tr>
</table>

When the bootstrap method is switched from that of `UpgradeModule` to
pure Angular, AngularJS ceases to exist on the page completely.
At this point, you need to tell Protractor that it should not be looking for
an AngularJS app anymore, but instead it should find *Angular apps* from
the page.

Replace the `ng12Hybrid` previously added with the following in `protractor-conf.js`:

<code-example format="">
  useAllAngular2AppRoots: true,
</code-example>

Also, there are a couple of Protractor API calls in the PhoneCat test code that
are using the AngularJS `$location` service under the hood. As that
service is no longer present after the upgrade, replace those calls with ones
that use WebDriver's generic URL APIs instead. The first of these is
the redirection spec:

<code-example path="upgrade-phonecat-3-final/e2e-spec.ts" region="redirect" header="e2e-tests/scenarios.ts">
</code-example>

And the second is the phone links spec:

<code-example path="upgrade-phonecat-3-final/e2e-spec.ts" region="links" header="e2e-tests/scenarios.ts">
</code-example>

### Unit Tests

For unit tests, on the other hand, more conversion work is needed. Effectively
they need to be *upgraded* along with the production code.

During TypeScript conversion no changes are strictly necessary. But it may be
a good idea to convert the unit test code into TypeScript as well.

For instance, in the phone detail component spec, you can use ES2015
features like arrow functions and block-scoped variables and benefit from the type
definitions of the AngularJS services you're consuming:

<code-example path="upgrade-phonecat-1-typescript/app/phone-detail/phone-detail.component.spec.ts" header="app/phone-detail/phone-detail.component.spec.ts">
</code-example>

Once you start the upgrade process and bring in SystemJS, configuration changes
are needed for Karma. You need to let SystemJS load all the new Angular code,
which can be done with the following kind of shim file:

<code-example path="upgrade-phonecat-2-hybrid/karma-test-shim.1.js" header="karma-test-shim.js">
</code-example>

The shim first loads the SystemJS configuration, then Angular's test support libraries,
and then the application's spec files themselves.

Karma configuration should then be changed so that it uses the application root dir
as the base directory, instead of `app`.

<code-example path="upgrade-phonecat-2-hybrid/karma.conf.ajs.js" region="basepath" header="karma.conf.js">
</code-example>

Once done, you can load SystemJS and other dependencies, and also switch the configuration
for loading application files so that they are *not* included to the page by Karma. You'll let
the shim and SystemJS load them.

<code-example path="upgrade-phonecat-2-hybrid/karma.conf.ajs.js" region="files" header="karma.conf.js">
</code-example>

Since the HTML templates of Angular components will be loaded as well, you must help
Karma out a bit so that it can route them to the right paths:

<code-example path="upgrade-phonecat-2-hybrid/karma.conf.ajs.js" region="html" header="karma.conf.js">
</code-example>

The unit test files themselves also need to be switched to Angular when their production
counterparts are switched. The specs for the checkmark pipe are probably the most straightforward,
as the pipe has no dependencies:

<code-example path="upgrade-phonecat-2-hybrid/app/core/checkmark/checkmark.pipe.spec.ts" header="app/core/checkmark/checkmark.pipe.spec.ts">
</code-example>

The unit test for the phone service is a bit more involved. You need to switch from the mocked-out
AngularJS `$httpBackend` to a mocked-out Angular Http backend.

<code-example path="upgrade-phonecat-2-hybrid/app/core/phone/phone.service.spec.ts" header="app/core/phone/phone.service.spec.ts">
</code-example>

For the component specs, you can mock out the `Phone` service itself, and have it provide
canned phone data. You use Angular's component unit testing APIs for both components.

<code-example path="upgrade-phonecat-2-hybrid/app/phone-detail/phone-detail.component.spec.ts" header="app/phone-detail/phone-detail.component.spec.ts">
</code-example>

<code-example path="upgrade-phonecat-2-hybrid/app/phone-list/phone-list.component.spec.ts" header="app/phone-list/phone-list.component.spec.ts">
</code-example>

Finally, revisit both of the component tests when you switch to the Angular
router. For the details component, provide a mock of Angular `ActivatedRoute` object
instead of using the AngularJS `$routeParams`.

<code-example path="upgrade-phonecat-3-final/app/phone-detail/phone-detail.component.spec.ts" region="activatedroute" header="app/phone-detail/phone-detail.component.spec.ts">
</code-example>

And for the phone list component, a few adjustments to the router make
the `RouteLink` directives work.

<code-example path="upgrade-phonecat-3-final/app/phone-list/phone-list.component.spec.ts" region="routestuff" header="app/phone-list/phone-list.component.spec.ts">
</code-example>
