Check all checkboxes after page load with jQuery

How to select all checkboxes while click on a checkbox after page load. For this my code is,

  $('#selectall').click(function () {
    if (this.checked) {
        $(':checkbox').each(function () {
            this.checked = true;
        });
      } else {
        $(':checkbox').each(function () {
            this.checked = false;
        });
    }
   });

This code is not working because I think the checkboxes are appearing after page load. How can I resolve this problem?