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jQuery Tiny Pub/Sub: A really, really, REALLY tiny pub/sub implementation for jQuery.
/* jQuery Tiny Pub/Sub - v0.7 - 10/27/2011
* http://benalman.com/
* Copyright (c) 2011 "Cowboy" Ben Alman; Licensed MIT, GPL */
(function($) {
var o = $({});
$.subscribe = function() {
o.on.apply(o, arguments);
};
$.unsubscribe = function() {
o.off.apply(o, arguments);
};
$.publish = function() {
o.trigger.apply(o, arguments);
};
}(jQuery));
/* jQuery Tiny Pub/Sub - v0.7 - 10/27/2011
* http://benalman.com/
* Copyright (c) 2011 "Cowboy" Ben Alman; Licensed MIT, GPL */
(function(a){var b=a({});a.subscribe=function(){b.on.apply(b,arguments)},a.unsubscribe=function(){b.off.apply(b,arguments)},a.publish=function(){b.trigger.apply(b,arguments)}})(jQuery)
@stof
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stof commented Dec 14, 2011

@cowboy I figured after commenting that what really broke the plugin was the missing ; at then end, which caused issues when concatenating files together

@cowboy
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Author

cowboy commented Dec 14, 2011

Your concatenating utility could join JavaScript source files on ";" instead of "".

@drewwells
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drewwells commented Dec 16, 2011

God help me how do I stop getting notifications on this thing?

@paulirish
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paulirish commented Feb 10, 2012

works in IE9+, or with Modernizr 2.5 or standalone Function.prototype.bind polyfill

(function($) {
  var o         = $({});
  $.subscribe   = o.on.bind(o);
  $.unsubscribe = o.off.bind(o);
  $.publish     = o.trigger.bind(o);
}(jQuery));

@eschwartz
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eschwartz commented Mar 15, 2012

Does anyone have any thoughts on using this pattern with Zepto? I've found that Zepto doesn't like $({}), though it's fine with $('<b/>'). Is this a significant performance hit to use $('<b/>'), or is there a better way to port this plugin to Zepto?

@rwaldron
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rwaldron commented Mar 15, 2012

@eschwartz $({}) is just an empty jQuery object, substitute it for whatever is the equivalent in Zepto

@eschwartz
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eschwartz commented Mar 15, 2012

@rwldrn Thanks, but my issue is that I haven't been able to figure out how to create an empty element in Zepto. I suppose I should pose that issue on a Zepto forum, but I thought someone might have a workaround here.

@javascripter
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javascripter commented Mar 26, 2012

Zepto only makes use of the DOM-based event system so there's no way to get a real empty element to work as the global pub/sub object. We might as well use ("").

@kodi
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kodi commented Oct 12, 2012

I wrapped this into AMD module to use it with require.js

define(function () {

    "use strict";

    /**
     *    Events. Pub/Sub system for Loosely Coupled logic.
     *    Based on Peter Higgins' port from Dojo to jQuery
     *    https://github.com/phiggins42/bloody-jquery-plugins/blob/master/pubsub.js
     *
     *    Re-adapted to vanilla Javascript
     *
     *    ----------------------------------------------------------
     *    And then wrapped to AMD Module by Dragan Bajcic @kodisha
     *
     *    @class Events
     */
    return {
        cache : {},
        /**
         *    Events.publish
         *    e.g.: Events.publish("/Article/added", [article], this);
         *
         *    @class Events
         *    @method publish
         *    @param topic {String}
         *    @param args    {Array}
         *    @param scope {Object=} Optional
         */
        publish : function (topic, args, /** {Object=} */ scope) {

            console.log('publish',topic, args);
            if (this.cache[topic]) {
                var thisTopic = this.cache[topic],
                    i = thisTopic.length - 1;

                for (i ; i >= 0 ; i -= 1) {
                    thisTopic[i].apply(scope || this, args || []);
                }
            }
        },
        /**
         *    Events.subscribe
         *    e.g.: Events.subscribe("/Article/added", Articles.validate)
         *
         *    @class Events
         *    @method subscribe
         *    @param topic {String}
         *    @param callback {Function}
         *    @return Event handler {Array}
         */
        subscribe : function (topic, callback) {

            console.log('subscribe', topic, callback);
            if (!this.cache[topic]) {
                this.cache[topic] = [];
            }
            this.cache[topic].push(callback);
            return [topic, callback];
        },
        /**
         *    Events.unsubscribe
         *    e.g.: var handle = Events.subscribe("/Article/added", Articles.validate);
         *        Events.unsubscribe(handle);
         *
         *    @class Events
         *    @method unsubscribe
         *    @param handle {Array}
         *    @param completly {Boolean}
         *    @return {type description }
         */
        unsubscribe : function (handle, completly) {
            var t = handle[0],
                i = this.cache[t].length - 1;

            if (this.cache[t]) {
                for (i ; i >= 0 ; i -= 1) {
                    if (this.cache[t][i] === handle[1]) {
                        this.cache[t].splice(this.cache[t][i], 1);
                        if (completly) {
                            delete this.cache[t];
                        }
                    }
                }
            }
        }
    };

});

@stsvilik
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stsvilik commented Oct 14, 2012

I have only one concern/suggestion to this relatively simple PubSub - it doesn't take into account published events that have already happened (in the past). Why is this important? Assume for a second that I want to subscribe to an event that had already happened, or I dont know that it happened, but still want my new subscriber to be triggered with the last-published values? My suggestion is to add something like this:

(function($) {

var o = $({}), pastEvents = {};

$.subscribe = function() {
var type = arguments.slice(0, 1)[0],
handler = arguments.slice(-1)[0];
//Fire your subscribe handler if event has already happened
if(type in pastEvents) {
pastEvents[type].done(function() {
handler.apply(o, arguments);
});
}
//Subscribe to future events as well
o.on.apply(o, arguments);
};

$.unsubscribe = function() {
o.off.apply(o, arguments);
};

$.publish = function() {
var type = arguments.slice(0, 1)[0],
data = arguments.slice(1)[0];
//Preserve data for future subscribers to this event
pastEvents[type] = $.Deferred().resolve(data).promise();
o.trigger.apply(o, arguments);
};

}(jQuery));

@chrisclarke1977
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chrisclarke1977 commented Jan 15, 2013

Even smaller just for sillyness

var o=$({}),s='subscribe';
$.each({on:s,off:'un'+s,trigger:'publish'},function(k,v){$[v]=function(){o[k].apply(o,arguments)};});

@zaus
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zaus commented Feb 11, 2013

If we're talking about relative sizes, why use "publish/subscribe" nomenclature? Just stick with "on/off/trigger" (or my preferred "on/off/do").

UPDATE I just found out why the "pros" stick to trigger instead of do (boo <IE9).

Example: https://gist.github.com/zaus/4756518

/* jQuery Tinier Pub/Sub - v0.9b - "on/off/do version" - 2013-02-11
 * original by http://benalman.com/ 10/27/2011
 * Original Copyright (c) 2011 "Cowboy" Ben Alman; Licensed MIT, GPL */

(function($) {

  // "topic" holder
  var o = $({});

  // attach each alias method
  $.each({on:0,off:0,"go":'trigger'}, function(alias,method) {
    $[alias] = function(topic, callbackOrArgs) {
        o[method || alias].apply(o, arguments);
    }
  });

}(jQuery));

@connected
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connected commented Feb 14, 2013

Is there a way i can e.preventDefault() on passed event? I ve tried it, but it doesn't work...

@zaus
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zaus commented Feb 19, 2013

@connected - what's the default event you're trying to prevent? isn't this limited to the arbitrary hidden topic var o? just curious.

@aghouseh
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aghouseh commented Apr 12, 2013

@kodi thanks for the requirejs module implementation!

@mediafreakch
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mediafreakch commented Jul 10, 2014

How would you add support for wildcards in the topic name? Does it even make sense as jQuery doesn't support wildcards for event names? Or is using a standalone pub/sub library the better approach?

@gmanish
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gmanish commented Dec 4, 2015

I know some javascript and little of jQuery (been playing with Ember, just for fun). I understand the on off methods, but I do not understand what var o = $({}); does. Can anyone please explain?

As always, google doesn't consider these braces and the $ in its search results.

@shshaw
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shshaw commented Apr 14, 2016

@gmanish var o = $({}) simply creates a jQuery collection with an empty object {} that becomes the recipient of all the event triggers. As other comments show, the recipient could be anything like $('<b />').

@Kiodaddy
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Kiodaddy commented Jun 20, 2017

I am telling you this is working really good.

@ahmed-musallam
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ahmed-musallam commented Aug 31, 2017

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