How to Run a Greasemonkey Script only once

Question

I made a greasemonkey script for a domain, Now how do I make it run only once? Like it starts every time the domain is accessed, I don't want that. How do I make it run only once and then like delete itself or make itself inactive?

Thanks.

Answer 1

If you want a script (or part of a script) to run only once, then you need to store a flag in non-volatile storage. A script cannot delete itself or turn itself off. But it can exit right away rather than run any other code.

To store things on a site-by-site (domain) basis, use localStorage. To store things on a script+namespace basis, use GM_setValue. Here's a basic script:

// ==UserScript==
// @name        _Run a GM script one-time only
// @namespace   _pc
// @include     http://YOUR_SERVER.COM/YOUR_PATH/*
// @grant       GM_getValue
// @grant       GM_setValue
// ==/UserScript==

var alreadyRun = GM_getValue ("alreadyRun",  false);

if ( ! alreadyRun) {
    GM_setValue ("alreadyRun", true);
    alert ("This part of the script will run exactly once per install.");
}

Answer 2

Redefine the function as the last statement in the body:

function foo()
 {
 ...
 foo = function(){};
 }