I have the following code in test.js which is run right before </body>:
alert('stovetop');
alert(greasy);
I have the following code in test.user.js:
(function () {
'use strict';
var greasy = 'greasy variable';
document.title = 'greasy title';
}());
'stovetop' gets alerted so I know the page javascript works, and document.title
gets changes so I know that the script javascript works. However, on the webpage I get the error:
Error: ReferenceError: greasy is not defined Source File: /test.js
How from the webpage do I access the variable set by Greasemonkey and how about vice versa?
You can also use localStorage:
localStorage.setItem("numberOfThings", "42");
localStorage.getItem("numberOfThings");
Your variable greasy
is defined in the scope of the anonymous function. You cannot access greasy
even in your userscript, unless it is part of your function. Example:
(function(){
var foo = 5;
alert(foo);
}();
alert(foo); //ERROR, because foo is undefined outside of the function.
Do it this way:
var foo = 5;
(function(){
alert(foo);
}();
alert(foo);
Also, why are you putting all your code in an anonymous function and then executing it?
Greasemonkey scripts operate in a separate scope and may also operate in a sandbox, depending on the @grant
settings.
Additionally, the question code isolates greasy
in a function scope (as gladoscc said).
Finally, by default, test.js will fire before the Greasemonkey script does, so it won't see any set variables, anyway. Use @run-at document-start
to address that.
So, given this test.js, run right before </body>
:
window.targetPages_GlobalVar = 'stovetop';
console.log ("On target page, local global: ", targetPages_GlobalVar);
console.log ("On target page, script global: ", gmScripts_GlobalVar);
Then the following will work:
No sandbox:
// ==UserScript==
// @name _Greasemonkey and target page, variable interaction
// @include http://YOUR_SERVER.COM/YOUR_PATH/*
// @include http://output.jsbin.com/esikut/*
// @run-at document-start
// @grant none
// ==/UserScript==
//--- For @grant none, could also use window. instead of unsafeWindow.
unsafeWindow.gmScripts_GlobalVar = 'greasy';
console.log ("In GM script, local global: ", unsafeWindow.targetPages_GlobalVar);
console.log ("In GM script, script global: ", gmScripts_GlobalVar);
window.addEventListener ("DOMContentLoaded", function() {
console.log ("In GM script, local global, after ready: ", unsafeWindow.targetPages_GlobalVar);
}, false);
With sandbox, no function scope, unsafeWindow
:
==> Important update: Greasemonkey changed unsafeWindow handling with version 2.0, the next sample script will not work with GM 2.0 or later. The other two solutions still work.
// ==UserScript==
// @name _Greasemonkey and target page, variable interaction
// @include http://YOUR_SERVER.COM/YOUR_PATH/*
// @include http://output.jsbin.com/esikut/*
// @run-at document-start
// @grant GM_addStyle
// ==/UserScript==
/*- The @grant directive is needed to work around a design change
introduced in GM 1.0. It restores the sandbox.
*/
unsafeWindow.gmScripts_GlobalVar = 'greasy';
console.log ("In GM script, local global: ", unsafeWindow.targetPages_GlobalVar);
console.log ("In GM script, script global: ", unsafeWindow.gmScripts_GlobalVar);
window.addEventListener ("DOMContentLoaded", function() {
console.log ("In GM script, local global, after ready: ", unsafeWindow.targetPages_GlobalVar);
}, false);
With sandbox, no function scope, Script Injection:
// ==UserScript==
// @name _Greasemonkey and target page, variable interaction
// @include http://YOUR_SERVER.COM/YOUR_PATH/*
// @include http://output.jsbin.com/esikut/*
// @run-at document-start
// @grant GM_addStyle
// ==/UserScript==
/*- The @grant directive is needed to work around a design change
introduced in GM 1.0. It restores the sandbox.
*/
function GM_main () {
window.gmScripts_GlobalVar = 'greasy';
console.log ("In GM script, local global: ", window.targetPages_GlobalVar);
console.log ("In GM script, script global: ", window.gmScripts_GlobalVar);
window.addEventListener ("DOMContentLoaded", function() {
console.log ("In GM script, local global, after ready: ", window.targetPages_GlobalVar);
}, false);
}
addJS_Node (null, null, GM_main);
function addJS_Node (text, s_URL, funcToRun, runOnLoad) {
var D = document;
var scriptNode = D.createElement ('script');
if (runOnLoad) {
scriptNode.addEventListener ("load", runOnLoad, false);
}
scriptNode.type = "text/javascript";
if (text) scriptNode.textContent = text;
if (s_URL) scriptNode.src = s_URL;
if (funcToRun) scriptNode.textContent = '(' + funcToRun.toString() + ')()';
var targ = D.getElementsByTagName ('head')[0] || D.body || D.documentElement;
targ.appendChild (scriptNode);
}
Notes:
unsafeWindow
and window
are the same.All of these scripts produce the same output on the console:
In GM script, local global: undefined
In GM script, script global: greasy
On target page, local global: stovetop
On target page, script global: greasy
In GM script, local global, after ready: stovetop
The Script Injection code will work in a variety of browsers besides Firefox. unsafeWindow
currently only works in Firefox+Greasemonkey(or Scriptish) or Chrome+Tampermonkey.
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