Javascript For Nested 'Select All' Checkboxes

I'm trying to display a list of checkboxes with a 'Select All' option for every item, and a 'Select All' item for each group. I have the following markup:

Solution 1:

Because you have both classes on that element

$(function () {
    $('.checkall').on('click', function () {
        $(this).closest('fieldset').find(':checkbox').prop('checked', this.checked);
    });
    $('.chkChild').on('click', function () {
        if (!$(this).is('.checkall')) {
            $(this).closest('fieldset').find('.checkall').prop('checked', false);
        }
    });
});

Demo: Fiddle