Using a Greasemonkey script to add javascript, from other sites, to a page

Question

Is it possible to use a Greasemonkey script to add in JS scripts from other sites to a page, so that they run?

possible duplicate of Including remote JS file via direct code injection with greasemonkey — Brock Adams
– Brock Adams, Commented Jan 13, 2013 at 1:06

Nemo64 · Accepted Answer · 2013-01-13 00:06:00Z

9

You can simply create a script element and add it to the document

// ==UserScript==
// @name       My Fancy New Userscript
// @description  enter something useful
// @match      http://*/*
// ==/UserScript==

(function () {
    var scriptElement = document.createElement( "script" );
    scriptElement.type = "text/javascript";
    scriptElement.src = "url to your script";
    document.body.appendChild( scriptElement );
})();

If you simply want the script to run then this is enough. If its a library like jQuery you want to use in your userscript it gets tricky. There are 2 ways that I'm aware of:

One is to use the require tag of greasemonkey.
The other one requires the same creation of a script element like shown above but you need to wait for it to load so scriptElement.onload = function () {} is needed and you'd have to use unsafeWindow to access variables from your library then.

I recommend the first method if this is a pure greasemonkey script because only than you script is encapsulated from the site.

answered Jan 13, 2013 at 0:06

Nemo64

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6 Comments

Brock Adams Over a year ago

+1 for @require. You don't need to wrap this code in an anonymous function.

Thomas Ward Over a year ago

Can I repeat using the variable scriptElement multiple times, to pull in multiple external javascripts? (such as script1.js and script2.js)

Thomas Ward Over a year ago

Also, is there a way to tell if this actually executes and adds this to the site(s)? Since it pulls in a script for me which will pull in live information and data from a remote .js script, and its not, hence my asking.

Nemo64 Over a year ago

@Lord Changing the src again means changing the value of the element in the document. I'd create multiple elements with multiple variables just to be safe.

Thomas Ward Over a year ago

That's what I figured, so i created three elements: scriptElement1, scriptElement2 and scriptElement3 and it all worked. And I figured out why its not pulling in the data - DNS resolution was borked, since I forgot to update the local DNS server information xD

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melpomene · Accepted Answer · 2013-01-12 23:51:56Z

0

Yes, you can do this for example:

let script = document.createElement('script');
script.src = "http://example.com/somescript.js";
document.body.appendChild(script);  // execute the script
document.body.removeChild(script);

answered Jan 12, 2013 at 23:51

melpomene

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2 Comments

fdrv Over a year ago

it doesnt work if i need load script from http for https

Peter Gerdes Over a year ago

Will this always execute the script? One doesn't need to wait for confirmation of execution before removing the child?

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