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jQuery Event Priority - Fusion Framework

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Aaron Scherer


jQuery, javascript, Javascript, programming

jQuery Event Priority - Fusion Framework

Posted by Aaron Scherer on .
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jQuery, javascript, Javascript, programming

jQuery Event Priority - Fusion Framework

Posted by Aaron Scherer on .

I've been working on a project at Underground Elephant that is a very very very heavy javascript project. Its heavily event driven, but I have an issue with the lack of event priorities in jquery. The Symfony 2 Event Listener is a great example of what an event listener should look like, for a couple reasons. First, and most importantly (to me at least), the events have a priority. Secondly, Events have specific classes that get passed with them, so you know exactly what to expect.

I wanted something like this for javascript, but there was really nothing out there for jQuery. In fact, Dave Methvin(@davemethvin), a member of the jQuery core team, made this comment about a year ago:

We've discussed this before and decided it's not productive to have handlers that try to out-prioritize each other. You're welcome to write something like that implementation as a plugin, as long as it's understood that it uses internals that may change and break the code.

This was a little disappointing to me, but I can understand a little why they made this decision.

So, with all this, I decided to make a small little addoon for jQuery that allows for creating custom events. The custom events can have priorties, and require a defined "class" (as javascript uses it).

Without further ado, i present to you: Fusion Framework

DISCLAIMER

As of right now, this framework only supports custom events.
You cannot use this for events that are meant to be bound to elements.

Requirements

This framework requires jQuery 1.9 or higher.

To Use

Creating Events

Right now, there are only two built in events. DOCUMENT_LOAD, and DOCUMENT_UNLOAD.
To use your own custom events, you need to add them to the event list, which can be done as follows:

( function( fusion ) {
    fusion.events.add( 'SOME_EVENT_NAME', fusion.event.extend( { somevar: null } ) );

    // You can store those in classes too. For example, the DOCUMENT_LOAD stuff
    var func = fusion.event.extend( {
        window: window,
        document: document
    } );

    fusion.events.add( 'DOCUMENT_LOAD', func );

} )( $.fn.fusion );

Binding Events (with priorities)

To bind to these events, we will be using the fuse method. Pretty simple, from the demo app:

You can get to the event's data with event.getData( [key] ).

// Note, by default $f is an alias of $.fn.fusion

// Create your first event. This has a default priority of 50.
$f.fuse( 'DOCUMENT_LOAD', function( event ) {
    event.getData( 'window' ).location.href += "#test";
} );

// Later down the line in your app, you want something bound before the above.
// So we create another bind, but set the priority to something lower than 50 (5 here).
$f.fuse( 'DOCUMENT_LOAD', function( event ) {
    event.getData( 'window' ).location.href += "#highesttest";
}, 5 );

// Even later down, we want something bound after the other two events.
// So we create another bind, but set the priority to something higher than 50 (70 here).
$f.fuse( 'DOCUMENT_LOAD', function( event ) {
    event.getData( 'window' ).location.href += "#test";
}, 70 );

You now have three binds on the DOCUMENT_LOAD event.

Firing Events

To fire these events, just call the ignite method, and pass in the event class's variables. Super simple.

For example, the DOCUMENT_LOAD and DOCUMENT_UNLOAD events.

$(function () {
    fusion.ignite( 'DOCUMENT_LOAD', { window: window, cheese: 'cheese' } );
    $( document ).unload( function( ) {
        fusion.ignite( 'DOCUMENT_UNLOAD', { window: window } );
    } )
});

If you noticed, as a test, I've added cheese: 'cheese' to the DOCUMENT_LOAD event, to see if you could access that on the page.
You can test this yourself, but in the binds, you wont be able to access the cheese data, because it was never in the class properties.

Contributions

If you would like to help with contributing, please do! Just fork this code, make your changes and put in a pull request.
I would love for this framework to work with element bound events, but I don't have enough time to figure that out.

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Aaron Scherer

http://aaronscherer.me