How to call a Greasemonkey function when a JavaScript link is clicked

Question

So I recently started working on Greasemonkey scripts without much prior experience in JavaScript. It was going fine until I hit this roadbloack.

I'm writing a script for a page that has a small table of information. If a link at the bottom is clicked, the table expands fully in the page to display all information. I need to call a function in Greasemonkey when this happens, however, the link doesn't appear to have an ID or anything I can actually reference to watch it. It's simply this:

<a href="javascript: expandFullTable(false);"></a>

When it's clicked, the table expands and it then shows as true. I initially used the following to expand the table upon loading the page, but that broke several things:

window.location.href = ('javascript: expandFullTable(false)');

I've attempted using "click", "onclick", and even "mouseover" to have Greasemonkey detect when it's pressed but nothing seems to work. From what I can tell it's simply a link that calls a function, but after some significant searching I wasn't able to find out anything about how to reference it in my script. I'm sure it's incredibly simple, but it's frustrated me to no end.

Answer 1

You can hijack the function like this:

var oldExpandFullTable = unsafeWindow.expandFullTable;
unsafeWindow.expandFullTable = function() {
    // Do something
    alert("You clicked on that thing!");

    // Call the original function
    oldExpandFullTable.apply(this, arguments);
};

But since you tagged this jquery this should let you retrieve the link:

var link = $("a[href^=\"javascript: expandFullTable\"]);

It should work if jQuery is injected into your script with @require . If it's already in the page, you can add this before to access it: var $ = unsafeWindow.jQuery; .

And by the way, perhaps you should learn more about unsafeWindow to avoid security holes.