Javascript closures (I think)

Question

I've got a piece of code I'm working with that was handed down to me by a previous developer. I am just trying to understand it better and not just use it naively. Here's the code:

slides.paginator.click(function (e) {
 e.preventDefault();
 interval.stop();
 switchSlide($(this).index());
 interval.start();
});

The part that I do not understand is the argument e that is being passed through this anonymous function. I have seen this before and I thought it had something to do with closures, but again, I am not sure. Can anyone give me a little insight into exactly how this parameter e works? I have seen it in other cases as well, such as with jQuery's AJAX methods.

Even pointing me in the right direction towards an article would be a great help. Thanks!

• Shanimal: This is the click event itself
• nhahtdh: A very general explanation (ignoring the fact that this is an event handler): You pass a function into the slides.paginator.click function. The slides.paginator.click will call your function when a click occurs. The e is simply parameter in the function that you pass in, and slides.paginator.click will supply the appropriate argument later.
• the system: "...how do I know that the click handler will provide such an event". By reading API documentation.
• the system: In the .click() docs, you'll see: .click( handler(eventObject) ) This is a description of the signature of the .click() method. It shows that it expects to receive a function to which an eventObject will be passed when invoked.
• David Hellsing: Here’s a link to the docs where jQuery explains all of it’s event object properties: api.jquery.com/category/events/event-object

Answer 1

"e" comes from "event", check the jquery .click() docs http://api.jquery.com/click/

function(e){} replaces "handler(eventObject)"

• Fillip Peyton: I see. Well, how do I know what is being passed in that eventObject that I can reference? I notice e.preventDefault(); is being called, which I know stops the default behavior from happening. Now that I think about it, maybe that's just it.
• arieljuod: cehck the docs for the eventObject api.jquery.com/category/events/event-object you can see the values and the methods you can call on it, you could use a browser inspector to watch the e object to understand it better
• Fillip Peyton: Yep, just ran across this as well. Your answer was exactly what I was looking for. Thanks for your help!