How can I get greasemonkey to call a function on a page after it loads

Question

I have a very simple greasemonkey script that I want to call an already existing javascript function on the page. I\'ve read the documentation and nothing seems to work

Answer 1

One way to call a function in the original page is like this:

location.href = "javascript:void(myFunction());";

It is a bit ugly. There is also the unsafeWindow provided by GreaseMonkey too, but the authors advise against using it.

unsafeWindow.myFunction();

Looks neater but make sure you understand the ramifications. From the manual:

unsafeWindow bypasses Greasemonkey's XPCNativeWrapper-based security model, which exists to make sure that malicious web pages cannot alter objects in such a way as to make greasemonkey scripts (which execute with more privileges than ordinary Javascript running in a web page) do things that their authors or users did not intend. User scripts should therefore avoid calling or in any other way depending on any properties on unsafeWindow - especally if if they are executed for arbitrary web pages, such as those with @include *, where the page authors may have subverted the environment in this way.

In other words, your script elevates the privileges available to the original page script if you use unsafeWindow.