js实现fieldset折叠

<fieldset>
<legend>单元1</legend>
<table cellPadding="1" cellSpacing="1" border="0"  class="panel-t">
<tr>
<td >
<input value="姓名">
<input value="年龄">
</td>
</tr>
</table>
</fieldset>

function initToggle() {
var legends = document.getElementsByTagName('legend');
for (var i = 0, len = legends.length; i < len; i++) {
legends[i].onclick = function () {//绑定事件
for (var j = 0, ln = this.parentElement.childNodes.length; j < ln; j++) {
var nodeName = this.parentElement.childNodes[j].nodeName;
if (nodeName && nodeName.toUpperCase() ===
'TABLE') {//兼容浏览器,有的浏览器childNodes的个数不同
var tbl = this.parentElement.childNodes[j];
if (tbl.style.display === 'none') {
tbl.style.display = 'block';
} else {
tbl.style.display = 'none';
}
}
}
}
}

}
document.onreadystatechange = function() { //页面加载完后，注册事件
if (document.readyState == "complete") {
initToggle();
}
}