js动态添加上传文件

我现在有个<a href="javascript:add()">添加上传文件<a/> 想点一下这个链接就出现一个添加上传文件的按钮
有人知道怎么做么？不用删除。就添加就行

解决方案 »

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>add radio</title>
   <meta http-equiv="pragma" content="no-cache">
   <meta http-equiv="cache-control" content="no-cache">
   <meta http-equiv="expires" content="0">
   <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
   <meta http-equiv="description" content="This is my page">
   </head>
<script type="text/javascript">
var i = 1;
function add(){
var n = 'sign'+i;
var b = Math.floor(Math.random()*100+1);
if(b<10){
   var1 = document.createElement("<input type='radio' name='"+n+"' value='1' checked />");
   var2 = document.createElement("<input type='radio' name='"+n+"' value='2' />");
   var3 = document.createElement("<input type='radio' name='"+n+"' value='3' />");
   }
   else if(b>10&&b<50){
   var1 = document.createElement("<input type='radio' name='"+n+"' value='1' />");
   var2 = document.createElement("<input type='radio' name='"+n+"' value='2' checked/>");
   var3 = document.createElement("<input type='radio' name='"+n+"' value='3' />"); }
   else {
   var1 = document.createElement("<input type='radio' name='"+n+"' value='1' />");
   var2 = document.createElement("<input type='radio' name='"+n+"' value='2' />");
   var3 = document.createElement("<input type='radio' name='"+n+"' value='3' checked/>");
   }
   var br1 = document.createElement("span");
   var br2 = document.createElement("span");
   var br3 = document.createElement("span");
   br1.innerHTML = "是";
   br2.innerHTML = "否";
   br3.innerHTML = "其他<br/>";

   var ra = document.getElementById("ra");
   ra.appendChild(var1);
   ra.appendChild(br1);

   ra.appendChild(var2);
   ra.appendChild(br2);

   ra.appendChild(var3);
   ra.appendChild(br3);
//    ra.appendChild("<br/>");
i++;
}
</script>
<body>
请点击下面的按钮添加radio button
<div id="ra"></div>
<input type="button" name="add" value="add" onclick="add();"/><br>
</body>
</html>
var newFile = document.createElement("<input type='file'/>");
document.body.append(newFile);
http://www.cnblogs.com/cloudgamer/archive/2009/12/22/ImagePreview.html
看看这个
http://www.cnblogs.com/cloudgamer/archive/2009/12/22/ImagePreview.html
<script type="text/javascript">
var flag=false;
function add(){
flag=true;
$("form").append("选择文件:<input type='file' name='model.files'/><br>");
}
</script>
jsp：
<input type="button" onclick="add()" value="新增上传"/>
<input type="button" onclick="return check()" value="上传所有"/>
<form id="form" name="form" action="upload.action" method="POST"  enctype="multipart/form-data">
</form>
jsmart里面有插件，去下一个，里面有的
<input type="file">呢，再加个按钮