CheckBox全选实现

<td style="width:80px">      <input id= "chkHeader" type= "checkbox" onclick= "selectall(this)"/>全选 </td>

<script type="text/javascript" language="javascript">    function selectall(chkcontrol) {        var chkall = chkcontrol;        State = chkall.checked;        elem = chkall.form.elements;        for (i = 0; i < elem.length; i++) {            if (elem[i].type == "checkbox" && elem[i] != chkall.id) {                if (elem[i].checked != State) {                    elem[i].click();                }            }        }    }</script>