Checkbox group (parent/children) functionality. Makes a checkbox parent of other checkboxes.

• If the parent is clicked the children are checked/unchecked based on the parent.
• If all the children are checked, parent gets checked too.
• If there is an unchecked item in the children and if the parent is checked, it gets unchecked.
• children can be a function. In this case, that function is run agaist the parent in order to find the children. This is useful for groups of checkboxes.
• Checks/unchecks parent based on the initial status of its children at start.

Example group usage:

$(".titles input:checkbox").cbFamily(function (){
  return $(this).parents("div:first").next().find("input:checkbox");
});

The plugin code:

;(function ($) {
    $.fn.cbFamily = function (children) {
        return this.each(function () {
            var $this = $(this);
            var els;
            if ($.isFunction(children)) {
                els = children.call($this);
            } else {
                els = $(children);
            }
            $this.bind("click.cbFamily", function () {
                els.prop('checked', this.checked).change();
            });

            function checkParent() {
                $this.prop('checked',
                    els.length == els.filter("input:checked").length);
            }

            els.bind("click.cbFamily", function () {
                if ($this.prop('checked') && !this.checked) {
                    $this.prop('checked', false).change();
                }
                if (this.checked) {
                    checkParent();
                    $this.change();
                }
            });

            // Check parents if required on initialization
            checkParent();
        });
    };
})(jQuery);