Learning jQuery

A common pattern in jQuery plugin development is the need to undo what the plugin has done. This is usually handled through a method prefixed with “un”. Another common pattern is the use of anonymous functions for event handlers. Unbinding events is easy with jQuery but unbinding a single event handler requires the use of a named function. jQuery 1.2 now provides another option for binding and unbinding events: event namespaces.

A Plugin

As a very simple example, let’s say I wrote a plugin called “clicked”. It provides two methods: clicked and unclicked. The clicked method attaches an event to all matched elements that when clicked adds a class name of “clicked” to the clicked element. The unclicked method removes the “clicked” classes it might have set and the clicked event handlers it attached. Here is the code:

[js](function($){
$.fn.extend({
clicked: function() {
return this.bind(‘click’, function() {
$(this).addClass(‘clicked’);
});
},
unclicked: function() {
retun this.removeClass(‘clicked’).unbind(‘click’);
}
});
})(jQuery);[/js]

You could use the plugin by calling it like this:

[js]$(‘div’).clicked();[/js]

And if you wanted to stop using the plugin, you could just call unclicked:

[js]$(‘div’).unclicked();[/js]

So far, so good.

A Problem

But let’s say I’m also using another plugin that attaches a click event to the same elements that the clicked plugin does. Calling unclicked would unbind all the click events, including those bound by your own code or another plugin.

A Solution: Event Namespacing

Event namespacing provides a way to manage specific event handlers. For example, a plugin could namespace its event handlers to make them easier to unbind while still using anonymous functions. To namespace an event, just suffix the event type with a period and a name (“type.namespace“).

Here is the clicked plugin again, but this time using event namespaces:

[js](function($){
$.fn.extend({
clicked: function() {
return this.bind(‘click.clicked’, function() {
$(this).addClass(‘clicked’);
});
},
unclicked: function() {
retun this.removeClass(‘clicked’).unbind(‘click.clicked’);
}
});
})(jQuery);[/js]

Now it only unbinds the events that it bound in the first place, leaving any other bound events alone.