input类型Checkbox复选款全选和取消

<script type="text/javascript">
function checkJs(boolValue) {
if (document.all.check2.length >= 1) {
for (var i = 0; i < document.all.check2.length; i++) {
document.all.check2[i].checked = boolValue;
}
} else {
document.all.check2.checked = boolValue;
}
}
</script>

<input type="checkbox" name="check1" onclick="checkJs(this.checked)" /><br />
<input type="checkbox" name="check2" /><br />
<input type="checkbox" name="check2" /><br />
<input type="checkbox" name="check2" /><br />
<input type="checkbox" name="check2" /><br />
<input type="checkbox" name="check2" /><br />
<input type="checkbox" name="check2" /><br />