function initPlaceHolders(){
    if('placeholder' in document.createElement('input')){ //如果浏览器原生支持placeholder
        return ;
    }
    function target (e){
        var e=e||window.event;
        return e.target||e.srcElement;
    };
    function _getEmptyHintEl(el){
        var hintEl=el.hintEl;
        return hintEl && g(hintEl);
    };
    function blurFn(e){
        var el=target(e);
        if(!el || el.tagName !='INPUT' && el.tagName !='TEXTAREA') return;//IE下，onfocusin会在div等元素触发
        var    emptyHintEl=el.__emptyHintEl;
        if(emptyHintEl){
            if(el.value) { emptyHintEl.style.display='none'; }
            else { emptyHintEl.style.display='block'; }
        }
    };
    function focusFn(e){
        var el=target(e);
        if(!el || el.tagName !='INPUT' && el.tagName !='TEXTAREA') return;//IE下，onfocusin会在div等元素触发
        var emptyHintEl=el.__emptyHintEl;
        if(emptyHintEl){
            //clearTimeout(el.__placeholderTimer||0);
            emptyHintEl.style.display='none';
        }
    };
    if(document.addEventListener){
        document.addEventListener('focus',focusFn, true);
        document.addEventListener('blur', blurFn, true);
    }
    else{
        document.attachEvent('onfocusin',focusFn);
        document.attachEvent('onfocusout',blurFn);
    }

    var elss=[document.getElementsByTagName('input'),document.getElementsByTagName('textarea')];
    for(var n=0;n<2;n++){
        var els=elss[n];
        for(var i =0;i<els.length;i++){
            var el=els[i];
            var placeholder=el.getAttribute('placeholder'),
                emptyHintEl=el.__emptyHintEl;
            if(placeholder && !emptyHintEl){
                emptyHintEl=document.createElement('span');
                emptyHintEl.innerHTML=placeholder;
                emptyHintEl.className='emptyhint';
                emptyHintEl.onclick=function (el){return function(){try{el.focus();}catch(ex){}}}(el);
                if(el.value) emptyHintEl.style.display='none';
                el.parentNode.insertBefore(emptyHintEl,el);
                el.__emptyHintEl=emptyHintEl;
            }
        }
    }
}
initPlaceHolders();