Question

Lets say I have a web app which has a page that may contain 4 script blocks – the script I write may be found in one of those blocks, but I do not know which one, that is handled by the controller.

I bind some onclick events to a button, but I find that they sometimes execute in an order I did not expect.

Is there a way to ensure order, or how have you handled this problem in the past?

Answer 1

I had been trying for ages to generalize this kind of process, but in my case I was only concerned with the order of first event listener in the chain.

If it’s of any use, here is my jQuery plugin that binds an event listener that is always triggered before any others:

** UPDATED inline with jQuery changes (thanks Toskan) **

(function($) {
    $.fn.bindFirst = function(/*String*/ eventType, /*[Object])*/ eventData, /*Function*/ handler) {
        var indexOfDot = eventType.indexOf(".");
        var eventNameSpace = indexOfDot > 0 ? eventType.substring(indexOfDot) : "";

        eventType = indexOfDot > 0 ? eventType.substring(0, indexOfDot) : eventType;
        handler = handler == undefined ? eventData : handler;
        eventData = typeof eventData == "function" ? {} : eventData;

        return this.each(function() {
            var $this = $(this);
            var currentAttrListener = this["on" + eventType];

            if (currentAttrListener) {
                $this.bind(eventType, function(e) {
                    return currentAttrListener(e.originalEvent); 
                });

                this["on" + eventType] = null;
            }

            $this.bind(eventType + eventNameSpace, eventData, handler);

            var allEvents = $this.data("events") || $._data($this[0], "events");
            var typeEvents = allEvents[eventType];
            var newEvent = typeEvents.pop();
            typeEvents.unshift(newEvent);
        });
    };
})(jQuery);

Things to note:

• This hasn’t been fully tested.
• It relies on the internals of the jQuery framework not changing (only tested with 1.5.2).
• It will not necessarily get triggered before event listeners that are bound in any way other than as an attribute of the source element or using jQuery bind() and other associated functions.