各种兼容的placeholder

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GB2312">
<title>验证Valid ----placeholder</title>
    <meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
    <style>
    span.emptyhint {color:#999;position:absolute;padding:3px;}
    </style>
</head>
<body>
<div id=doc3>
    <div id="bd" >
        <div class="section-ctn">
            <ul>
                <li>
                    <label class="k">订单主人：</label>
                    <input type="text" placeholder="请填写订单主人" value="JK">
                </li>
                <li>
                    <label class="k">订单号：</label>
                    <input type="text" placeholder="请填写订单号">
                </li>
                <li>
                    <label class="k">备注：</label>
                    <textarea type="text" placeholder="请填写备注"></textarea>
                </li>
            </ul>
        </div>
    </div>
    <div id="ft">
        部分内容来自 qwrap wagang组件Valid: (<a href="http://dev.qwrap.com/resource/js/wagang/_index.html">http://dev.qwrap.com/resource/js/wagang/_index.html</a>)
    </div>
    <div id="ft">
        QWrap网址： <a href="http://www.qwrap.com">www.qwrap.com</a>
    </div>
</div>
</body>

<script>

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){
            //clearTimeout(el.__placeholderTimer||0);
            //el.__placeholderTimer=setTimeout(function(){//在360浏览器下，autocomplete会先blur再change
                if(el.value) emptyHintEl.style.display='none';
                else emptyHintEl.style.display='';
            //},600);
        }
    };
    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){//ie
        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();

</script>
</html>

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原文地址：https://www.cnblogs.com/hubing/p/3473425.html