Simple select unselect all

I have a simple html table, every row in tbody has a checkbox. thead has a checkbox. When it is checked/unchecked, all checkboxes have to be selected/ unselected. Here is a very simple javascript to achieve this:

$("#mytable thead :checkbox").live({
  change: function () {
    var checked = $(this).is(":checked");
    $("#mytable tbody :checkbox").attr("checked", checked);
  }
});

• javascript
• jQuery
• simple