How to inject javascript into page, from a Firefox add-on, and run it?

Question

I\'m writing a Firefox extension (add-on) to allow users to annotate any page with text and/or drawings and then save an image of the page including the annotations. Use cas

Answer 1

Use the Greasemonkey extension :

Allows you to customize the way a web page displays or behaves, by using small bits of JavaScript.

Hundreds of scripts, for a wide variety of popular sites, are already available at http://userscripts.org.

You can write your own scripts, too. Check out http://wiki.greasespot.net/ to get started.

Answer 2

So this is how I solved my problem by setting the onload attribute to call the init function in the script that's being appended to the page.

var myScript = top.window.content.document.createElement('script');
myScript.type = 'text/javascript';
myScript.setAttribute('src','chrome://path/to/script.js');
myScript.setAttribute('onload', 'firefoxInit()');
top.window.content.document.getElementsByTagName('head')[0].appendChild(myScript);