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How to Profile Greasemonkey Scripts with Firebug

Posted in Firefox and Greasemonkey, Programming Tools, Technology by engtech on November 13, 2007

Programming Tips

Running performance analysis on Greasemonkey scripts can be a pain in the butt. They aren’t part of a webpage so standard tools for analyzing web sites don’t work… or do they?

The Goal

Profiling Greasemonkey scripts with Firebug

What You’ll Need

  1. Firefox
  2. Greasemonkey
  3. Firebug extension

The Trick

#1: You need to remove all of the Greasemonkey GM_* functions from the script you want to profile. This is easier than it sounds because all of the functions can be performed by plain ‘ole javascript (except for the open in new tab function and register menu command).

#2: You need to embed your Greasemonkey script inside of the running page so you can analyze it with Firebug’s profile tool. I have a function below that can embed a function inside the current web page.

#3: You’ll need to call the function either using unsafeWindow or by embedding a call to the function in the page.

#4: Litter your code with calls to Firebug’s console.profile() and console.time() functions.

Sample Code Template

(function() {
  function embedFunction(s) {
document.body.appendChild(document.createElement('script')).innerHTML =

  function myKickassGreasemonkeyScript() {
    // Put everything you need for your Greasemonkey script in here
    // Don't use any of the GM_* functions!

function kickass() {
      // Block of code that might take a lot of time
      // another block of code



// more cowbell


  // Method 1: embed the function call into the current page
  document.body.appendChild(document.createElement('script')).innerHTML = "myKickassGreasemonkeyScript();";
  // Method 2: directly call the function using unsafeWindow
//     window.addEventListener("load", function(e) {
//                   unsafeWindow.myKickassGreasemonkeyScript();
//                   this.removeEventListener('load',arguments.callee,false);
//                 }, false);


Firebug Tutorial

Michael Sync has a tutorial on using Firebug that describes the console.time() and console.profile() functions. The official website has a nice list of Firebug keyboard shortcuts and a brief description of all the console.* functions.

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