This is useful when you want to augment an existing event with additional functionality, which brings us to our first example:. Fortunately, the special events API can be used to make this automatic. Take a look at the code below, and then view the working example.
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At its core, the tripleclick event is powered by the click event. Click three times within a certain time threshold, and the tripleclick event fires. Also, this custom event is made possible by event delegation. After that point, whenever an element on the page is clicked, the event will propagate up the DOM tree to document, where the document click event handler will execute.
Since that handler can use event. In addition, the tripleclick event is only actually triggered on event. Because Internet Explorer is super-extra-awesome, you will need to click five times for the tripleclick event to fire, due to the way it triggers the click event when selecting text.
This example is similar to the previous example , with one major difference. One very important thing to note about this approach is that because the tripleclick event is being triggered explicitly on each element instead of being triggered only on event. This is an unfortunate side-effect of utilizing this per-element event-data approach. Of course, it could be, if the special events API were involved, so I recently created a jQuery resize event plugin to provide that functionality.
So, in this example, for each element to which a resize event handler is bound, a polling loop is started which periodically checks for dimension changes and triggers the event when appropriate. And thanks to the setup and teardown methods, the polling loop can be started only once the event is actually bound to an element, and can be stopped when all resize events are unbound from that element.
Sending Custom Events
See the next special event example, custom resize event: Whereas the previous example used one polling loop per element, this example uses a single polling loop for all elements. In this example, the elems variable contains a collection of all elements to which the event is bound, that is iterated over each time the polling loop function executes.
Note that while the overall structure of this special event example is the same as the finished plugin, some additional logic had to be written to prevent double-firing of event handlers when the event was manually triggered. See my jQuery resize event plugin for the complete, finished source. The add and remove methods, added in jQuery 1. The single handleObj argument passed into these methods contains a number of useful properties , most useful of which is the handler method.
This is the event handler being bound to the event, which is what gets called every time the event is triggered.
Ben Alman » jQuery special events
Using the add method to override the originally bound event handler with a new method, we can add in a little bit of extra logic that works for every click event in a completely unobtrusive way. Right now, in Internet Explorer 8, Firefox 3.
In addition, I have split the special event functionality such that while my jQuery hashchange event plugin actually creates the event, my jQuery BBQ plugin augments that event with an additional property and method, among other things. Whenever an event is triggered on an element, the event. Because of this, only the eventData value specified in that first bind call is utilized, so if you wanted to bind multiple handlers to the same element, each with its own click threshold, you were out of luck.
Well, because the add method is called for each bound event handler, it is possible to use the aforementioned eventData argument again, see the official bind method documentation on a per-handler basis, instead of on a per-element basis like using only the setup method allows. Since each handler now has its own threshold, clicks counter and last-clicked timestamp, this ultimately makes the event far more flexible.
Since bubbling up the DOM tree is an expected behavior for events, you may ultimately decide to keep it simple as in the original tripleclick event example , but that decision is up to you. Providing a default action for events offers another way in which a framework or plugin developers can abstract complex internals away from the end-user, allowing for simpler, more maintainable code.
jQuery special events
Now, while the framework provides the default action, which is responsible for handling all the internal framework-level nuances of removing a widget, the implementation-specific code is responsible for deciding when the default behavior should be prevented, if at all. When a bound event handler executes, this inside that handler always refers to the element on which the event was bound.
Here is the latest version: To your point, attribute selectors are relatively slower, but I wouldn't say slow. Looking at the benchmarks, they can still complete thousands if not tens of thousands of times per second. Selector execution is rarely the bottleneck of a web app, since they typically only run once for setup or upon some user action.
Unless you're spamming selectors non-stop not a good idea then the extra milliseconds won't amount to much. It doesn't work as a selector though. I thought that was likely the case. It's just that selecting elements via the attribute is pretty ugly:. Effective Event Binding with jQuery. A Better Selector Strategy Let's start with a basic example. Here's the HTML for a nav menu that can be toggled on or off: Will's passion for web development started with GeoCities and hasn't stopped since.
He currently works as an interactive developer in downtown Seattle. Note that there appears to be a bug with. The following code demonstrates:.
- Binding multiple events at once.
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- Some Syntactic Sugar?
The setTimeout call delays the unbinding and is supposed to remove the event binding on the foo function. Oddly the following that removes only one of the two handlers works:.