How to unselect selectall checkbox if any of the check box is unselected?

I've a check all checkbox where it check all the checkboxes once it is checked and vice-versa for uncheck .

How to uncheck the check all checkbox if any of the checkbox is unselected and check the check all check box if all the checkboxes are selected.

HTML

<form action="#">
    <p><label><input type="checkbox" id="checkAll"/> Check all</label></p>

    <fieldset>
        <legend>Loads of checkboxes</legend>
        <p><label><input type="checkbox" /> Option 1</label></p>
        <p><label><input type="checkbox" /> Option 2</label></p>
        <p><label><input type="checkbox" /> Option 3</label></p>
        <p><label><input type="checkbox" /> Option 4</label></p>
    </fieldset>
</form>

JavaScript

$("#checkAll").change(function () {
    $("input:checkbox").prop('checked', $(this).prop("checked"));
});

Fiddle demo