Poll for changes to element selects in Craft CMS

elementSelectChange.js

$(function () {

    // Bind a greedy event handler
    $('body').on('elementselectchange', '.elementselect', onElementSelectChange);

    // Poll to evalute elementselects every 10ms
    setInterval(evaluateElementSelects, 10);

    function evaluateElementSelects ()
    {
        var elementSelect,
            elementIds;
        $('.elementselect').each(function () {
            elementSelect = $(this).data('elementSelect');
            elementIds = $.map(elementSelect.$elementsContainer.children(), function (element) {
                return $(element).data('id');
            }).join('|');
            if (elementIds !== elementSelect.$container.data('elementIds')) {
                elementSelect
                    .$container
                        .data('elementIds', elementIds)
                        .trigger('elementselectchange');
            }
        });
    }

    function onElementSelectChange (e)
    {
        var $elementSelect = $(e.currentTarget);
        console.log('element select changed in some way', $elementSelect, $elementSelect.data('elementIds'));
    }

});