js实现checkbox全选

jsp页面代码：

<script src="${basepath}/js/common.js" type="text/javascript"></script>
<table>
    <thead>
        <tr>
            <th>
                <input type="checkbox" id="chk_all" name="chk_all" onclick="javascript:checkAll(this,'ids');" />
                 全选
            </th>
	</tr>
	</thead>
    <tbody>
	<tr>
            <td><input type="checkbox" value="${product.pId}" name="ids" id="ids" /></td>
				
	</tr>		
    </tbody>
</table>

js代码：

function checkAll(e, itemName)
{
    var aa = document.getElementsByName(itemName);
    for (var i = 0; i < aa.length; i++)
        aa[i].checked = e.checked;
}