Select/Deselect All Checkboxes

HTML

<label>
  <input type="checkbox" name="sample" class="selectall" /> Select all</label>

<div id="checkboxlist">

  <label>
    <input type="checkbox" name="sample[]" /> This is a checkbox1</label>
  <br />
  <label>
    <input type="checkbox" name="sample[]" /> This is a checkbox2</label>
  <br />
  <label>
    <input type="checkbox" name="sample[]" /> This is a checkbox3</label>
  <br />
  <label>
    <input type="checkbox" name="sample[]" /> This is a checkbox4</label>
  <br />

</div>

CSS

div {
  color: #C00;
  font-family: Tahoma, Geneva, sans-serif;
  font-size: 10px;
  margin-top: 10px;
  width: 500px;
}

input {
  padding-right: 10px;
}

JavaScript

$('.selectall').click(function() {
  if ($(this).is(':checked')) {
    $('div input').attr('checked', true);
  } else {
    $('div input').attr('checked', false);
  }
});