[JS] 清空file控件(兼容IE,火狐)

来源：http://yuanyong.javaeye.com/blog/654292

<script>
function cleanFile(id){
    var _file = document.getElementById(id);
    if(_file.files){
        _file.value ="";
    }else{
        if (typeof _file !="object"){ returnnull; }
        var _span = document.createElement("span");
        _span.id ="__tt__";
        _file.parentNode.insertBefore(_span,_file);
        var tf = document.createElement("form");
        tf.appendChild(_file);
        document.getElementsByTagName("body")[0].appendChild(tf);
        tf.reset();
        _span.parentNode.insertBefore(_file,_span);
        _span.parentNode.removeChild(_span);
        _span =null;
        tf.parentNode.removeChild(tf);
    }
}
</script>
<input id="file1" type="file"/>
<input type="button" value="清空" onclick="cleanFile('file1')"/>