Replace page functions with similar, but modified, userscript functions

Question

I am creating a userscript for a game that will modify certain parts of a page in real time to help the user know how long they must wait to perform certain actions.

The problem I am running into is that the game has some AJAX already built in, every three seconds it calls the jQuery.getJSON() function to grab information to update things. My script needs to make it appear to the end user as if the page was updating in real time, rather than every 3 seconds. As well as add extra information. Without adding extra requests (the games owners will not like that).

To do this I need to override the default behavior of the page, I need to change the callback function of the jQuery.getJSON() call to add my functionality. Or at least disable it completely so I can write a new one. And it isn't as easy as assigning a new function to the old name, as it has no name, they just build the function within the jQuery.getJSON() call. Is this possible?

The page script is contained in a separate .js file btw, if that makes any difference.

Jason M. Batchelor · Accepted Answer · 2012-10-10 17:16:18Z

1

If the jQuery.getJSON() call is assigned to a variable, it will return a jqXHR object, which you can then modify by adding or changing its callbacks.

If it is not exposed as a variable, but instead is simply called like so

... js blah ...
jQuery.getJSON("myurl",function(){
    more blah
});
... more blah ...

... then I believe you're up a creek without a paddle, as that becomes an anonymous function call with no handle. The only way, at that point, would be to try to override by loading another script in place over the first one, but I am really uncertain how stable that would leave the browser environment.

See the jQuery reference for http://api.jquery.com/jQuery.getJSON/ and http://api.jquery.com/Types/#jqXHR for more details on how the $.ajax() system works.

answered Oct 10, 2012 at 17:16

Jason M. Batchelor

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