jquery实现checkbox全选、取消全选

<input type="checkbox" name="checkbox_name[]" id="checkbox_name_1" />1<br />
<input type="checkbox" name="checkbox_name[]" id="checkbox_name_2" />2<br />
<input type="checkbox" name="checkbox_name[]" id="checkbox_name_3" />3<br />
<input type="checkbox" name="checkbox_name[]" id="checkbox_name_4" />4<br />
<input type="checkbox" name="checkedAll" id="checkedAll"/>全选/取消全选<script type="text/javascript"> 
<!-- 
j_q(function() { 
 j_q("#checkedAll").click(function() {  
 if (j_q(this).attr("checked") == true) { // 全选 
j_q("input[@name='checkbox_name[]']").each(function() { 
  j_q(this).attr("checked", true); 
  }); 
 } else { // 取消全选 
 j_q("input[@name='checkbox_name[]']").each(function() { 
 j_q(this).attr("checked", false); 
  }); 
 } 
 }); 
}); 
//--> 
</script>