一个动态产生控件的问题

[maybe198376]

做一个多文件上传的系统，需要动态产生文件域，就像hotmail那样，点击一个按钮，出来一个文件域，如何实现？

[Ryo_Hazuki]

<span id="test"></span>
<input type="button" onclick="test.innerHTML += '<input name=n>';">

[maybe198376]

var sequence = 0;
function addAttachment() {
var index = sequence++;
var area = document.getElementById("attach_area");
area.innerHTML +=
"<div id=\"attach_" + index + "\">" +
"<input name=\"attach_file_"+index+"\" type=\"file\" />" +
"<input type=\"button\" value=\"删除\" onclick=\"removeAttachment("+index+")\">" +
"</div>";

}

function removeAttachment(index) {
var attachment = document.getElementById("attach_"+index);
if (attachment == null) {
return;
}
attachment.innerHTML = "";
attachment.outerHTML = "";
}
这是JS代码

[maybe198376]

<div id="attach_area">
</div>
<input type="button" value="添加附件" onclick="addAttachment()"/>
这是html片断，为什么，无论我添加几个附件index的一直是1？？？？