What real purpose does $.noop() serve in jQuery 1.4?

Question

Pouring over the release notes regarding jQuery 1.4, I came acrosss $.noop() which is:

Description: An empty function. (added in 1.4)

Answer 1

The only logical reason is if you're calling a function that does something AND calls another function, and you want the higher-level function to do its thing without calling a parameter function.

Most of the jQuery functions optionally take a parameter function, so you don't have to pass one in. Maybe there's one or two where that's not the case -- or maybe it's to assist developers with their custom code that behaves like this.

Answer 2

It can be useful if you have a function that supplies functions to other functions.

Example: You have a List of data. Each item has a Button that does something. The "something" can be different for every item. You have a "FunctionFactory" that takes in the item and returns a function. If you don't want the button to do something for whatever reason, then the cleanest way could be to return an empty function, as that way you know that your Factory ALWAYS returns a function.

I don't have a concrete example for jQuery, but I guess this could come in handy when used in an .each or .map block.

Answer 3

This function was proposed due to performance issues on embedded systems when using $.ajax, reported on the jQuery-Dev mailing list. You can see the thread.

Basically, they preferred to introduce and use this single empty function, rather than declaring empty anonymous functions all around.

Now this function is internally used in the ajax, event and offset modules.

You can give a look to the commit when it was introduced also.

Answer 4

Probably if some bad API requires a function as a parameter, and you don't want to do anything in it, this would be a framework-supported way of making that obvious.

Answer 5

If you have a function that accepts a function as a parameter, and you don't have any code to give it, you can pass $.noop.

I can't think of any such cases in jQuery where the parameter isn't optional in the first place, though.

Unlike writing function(){}, passing $.noop will not create a new function instance, saving a bit of memory. However, if whatever you're passing it to modifies the function object (eg, funcParam.id = 2), passing $.noop will mess things up.

Answer 6

If a function requires you pass a function as an argument maybe? It's shorter to say do_something($.noop) than do_something(function(){}).

Although not by much...

...6 characters...

...yeah, that feature looks quite useless actually.