MediaWiki

Gadget kitchen

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Welcome to the gadget kitchen. This is a tutorial for how you can write and use gadgets and user scripts in JavaScript.

What are user scripts and gadgets?

MediaWiki allows anyone to write public JavaScript code to immediately change the behavior of the software. This code can be shared with other users. This code is located in wiki pages.

  • A user script can be edited by the original author (if it is stored in the User: namespace) and by anyone with the "edituserjs" user right (usually just interface administrators). The code is usually hosted on a subpage of your user page. Examples include: XTools/ArticleInfo.js and m:User:Hoo man/useful links.js. User scripts are similar to the personal JavaScript pages such as Special:MyPage/common.js, but they allow single code chunks to be shared with other users.
  • A gadget is a user script which has been "promoted" by an interface administrator, by adding it to MediaWiki:Gadgets-definition. Logged-in users can enable gadgets in the "Gadgets" tab of their user preferences. Gadgets are created and managed by interface administrators.
  • For completeness: There is also the site-wide JavaScript located at MediaWiki:Common.js and several other pages. The JavaScript in those pages affects everyone and is executed automatically for both logged-out and logged-in users. Interface administrators can edit them. Read Manual:Interface/JavaScript for detailed information.

If you're running your own copy of MediaWiki, $wgAllowUserJs needs to be enabled for user scripts to work, and the Gadgets extension needs to be installed to make it possible to promote individual scripts to gadget status. For a nicer development experience, ensure that the CodeEditor extension is installed on your wiki.

Write your first user script

In this section, you create an example user script which calculates the estimated reading time of a wiki page.

  1. Ensure you are logged in.
  2. Visit Special:MyPage/common.js. This page holds your personal JavaScript that is loaded on every page view (except for Special:Preferences).
  3. Either create the page or edit the page if it already exists.
  4. Copy the following six lines and paste these lines into the page: 
    var numWords = $("#mw-content-text > div").text().split(" ").length;
var headerWords = $("h1").text().split(" ").length;
var totalWords = numWords + headerWords;
var timeInMinutes = totalWords / 200;
var header = $("h1").text();
$("h1").text(header + " (it will take you " + timeInMinutes + " minutes to read this page)");
  5. Click "Publish changes".
  6. Go to any page. Look at the title.

This example user script is taken from ChickTech High School Kickoff 2017/Tasks . There are more examples for simple user scripts on that page.

A more complex user script example

Check out MediaWiki:Tutorial-QuickRC.js which uses mw.loader, mw.util, mw.html, mw.user from ResourceLoader, the MediaWiki Action API, a jQuery UI dialog, jQuery AJAX, and jQuery event binding.

Copy and paste the contents of MediaWiki:Tutorial-QuickRC.js into your Special:MyPage/common.js.

The result should be the same as above, but now you can modify the script, play with it, and replace it with something else entirely.

Clicking "Preview" (or using the keyboard shortcut, typically ⇧ Shift+Alt+P) in the editor will also execute the latest version of the script. This is a good way to iterate without saving the page. Remember, nothing is saved until you press "Publish page".

Load an existing user script

In the previous section, you copied the content of a user script. In this section, you will load the existing script MediaWiki:Tutorial-QuickRC.js instead.

  1. Ensure you are logged in.
  2. Visit Special:MyPage/common.js. This page holds your personal JavaScript that is loaded on every page view (except for Special:Preferences).
  3. Either create the page or edit the page if it already exists.
  4. Copy the following text and paste it into the page: 
    mw.loader.load('//www.mediawiki.org/w/index.php?title=MediaWiki:Tutorial-QuickRC.js&action=raw&ctype=text/javascript');
  5. Click "Publish changes". You should now have a link in the "Tools" section called "Quick changelog".
  6. Click "Quick changelog". You get a pop-up window. It shows you a subset of the recent changes on this website.

Use a script on another Wikimedia wiki

If you want to use a script on another Wikimedia website (for example English Wikipedia instead of MediaWiki.org), you perform the same steps as above: you tell ResourceLoader to load your code. Visit your common.js on English Wikipedia, and add the following: 

mw.loader.load("//www.mediawiki.org/w/index.php?title=MediaWiki:Tutorial-QuickRC.js&action=raw&ctype=text/javascript");

You can also load the user script which you just created above, by changing MediaWiki:Tutorial-QuickRC.js in the previous line to User:YourName/YourScript.js (replace YourName and YourScript accordingly). This first requires that you do not store the code of your user script in Special:MyPage/common.js itself but instead in a separate sub page of your user page.

This also helps to keep code in one single place, so you have to update code in only one place.

Developing user scripts and gadgets

This section lists resources which are either needed or helpful for non-simple user scripts.

ResourceLoader

Gadgets must use ResourceLoader. ResourceLoader is a core feature of MediaWiki that intelligently delivers JavaScript and CSS assets to users and readers. Because Gadgets are coded in JavaScript, as a Gadget coder you're bound to interact with ResourceLoader.

Your gadget should load useful ResourceLoader modules.

OOUI

OOUI is a JavaScript library with user interface elements (for example pop-up windows) specifically for use in MediaWiki. The library Using OOUI in MediaWiki#Gadgets can be used in gadgets.

MediaWiki Action API

Within the context of a MediaWiki website the Action API can be accessed from JavaScript via the mw.Api JavaScript API. (mw.ForeignApi for allowed cross-site requests, e.g. between WMF wikis.) See API for more information.

If your gadget makes API requests directly, add the "?callback=?" parameter to the API URL if you are trying to make an API request that would violate the same-origin policy (e.g. making a request to the Commons API from Wikipedia). This triggers the use of JSONP and enforces certain restrictions.

VisualEditor

See VisualEditor/Gadgets for a tutorial specifically for VisualEditor gadgets.

Debugging user scripts and gadgets

Privacy and external content

You should not load external resources that may harm users privacy. In Wikimedia wikis, the following domains are considered safe:

  • *.wiktionary.org
  • *.wikimedia.org
  • *.wikibooks.org
  • *.wikisource.org
  • *.wikiversity.org
  • *.wikinews.org
  • *.wikiquote.org
  • *.wikidata.org
  • *.wikivoyage.org
  • www.mediawiki.org
There was a Jenkins job (job code) that automatically checked gadgets for this principle, but this job has not been actively run since 2022.

Running code on page load

The common task of running code as soon as the page is loaded has several pitfalls which even experienced editors fall into.

  • First of all, when your code works with elements of the DOM, run it on page load. Otherwise, your code may run too early. The general way to do it is to use jQuery's $() function, which does the same as $(document).ready().
  • However, if your code works with the content part of the page (the #mw-content-text element), you should use the 'wikipage.content' hook instead. This way your code will successfully reprocess the page when it is updated asynchronously and the hook is fired again. There are plenty of tools which do so, ranging from edit preview to watchlist autoupdate.
  • Be sure to only work with the descendants of the $content element that your handler function takes and not the whole page. Otherwise, you may end up running the same code for the same elements many times. Note that the 'wikipage.content' hook may be fired really many times.
  • Be cautious about what comes in the $content argument of the handler function. You shouldn't assume it's the #mw-content-text element. It can be a small portion of the page, e.g. when it is previewed.

Code that works with page content and avoids the aforementioned pitfalls may look like this: 

mw.hook( 'wikipage.content' ).add( function ( $content ) {
	const $target = $content.find( '.targetClass' );
	if ( $target.length ) {
		// Do things with $target
	}

	// Only perform some operations when it is #mw-content-text in the argument
	if ( $content.is( '#mw-content-text' ) ) {
		const $note = $( '<div>' )
			.addClass( 'myScript-note' )
			.text( 'MyScript has successfully processed the content!' );
		$content.prepend( $note );
	}
} );

If your code works with page content and adds event handlers to DOM elements, then, instead of hooking to 'wikipage.content' and looking for elements to attach event listeners to when it is fired, you may attach one event listener to an element outside of the content area or the whole document but filter events by a selector (see jQuery's documentation). That is, instead of writing $content.find( '.targetClass' ).on( 'click', ... ) you can write $( document ).on( 'click', '.targetClass', ... ).

Recording metrics

Some gadgets are serious business. When your gadget gets serious, you might want to instrument it for analytics purposes, for example to measure the click rate of specific UI elements added to a page by the gadget.

Main page: Gadget kitchen: recording metrics


Miscellaneous

Disadvantages and problems of gadgets

  • Gadgets are developed by community members. As of today, there is no formal code review required for gadgets on Wikimedia sites (see phab:T71445). Please follow the best practices listed on this page.
  • On Wikimedia sites, the process how to "promote" a user script to a gadget in the "Gadgets" tab of the user preferences is not always clear. You will have to find an interface administrator and might have to provide deployment instructions to them.
  • Wikimedia lacks a systematic process for re-using, modifying and contributing to existing user scripts and gadgets.

Ideas what to work on

Some Wikimedia community members may share their ideas what they would like to see implemented by someone else.

Deploying or enabling a gadget

If your user script should become a gadget (see the definitions above) on a wiki, the following steps are needed:

  • Steps for the user script author:
    • Recruit an experienced developer to review your gadget code. There is no formal process to do so.
    • Check with community members if there aren't any concerns with enabling the gadget on a wiki. For the website MediaWiki.org itself, this would be Project:Village Pump.
    • Recruit a site administrator with interface rights. See the page Special:ListUsers/interface-admin on your wiki.
  • Steps for the interface administrator:
    • Copy your JS & CSS files in the MediaWiki: namespace on your wiki, and make sure the page names have the prefix Gadget-.
      Example: MediaWiki:Gadget-userfeedback.js
    • Define the gadget on the MediaWiki:Gadgets-definition page of your wiki. That includes the modules used, dependencies, JS, and CSS file names, etc. This will allow users to enable the gadget on the Special:Preferences page of your wiki.
      Example: userfeedback[ResourceLoader|default|dependencies=ext.eventLogging]|userfeedback.js|userfeedback.css
    • Create a page for the gadget in the MediaWiki: namespace with prefix Gadget-. This will generate a label for the gadget on the Special:Preferences page of your wiki.
      Example: MediaWiki:Gadget-userfeedback

Contributing to user scripts

If a user script is made by another user you may be able to contribute to it. You can do this by making a copy of the user script as a subpage of your own user page. Then replace the original user script you had enabled with the one that is a user page in your common.js. Proceed to make edits as you please to your copy of the script. If you want the script to contain the changes you made to your copy of the script, you should ping the author of the script on the discussion page of the original user script with the page that contains your changes and ask them to add the changes. If the user is no longer active, then you should notify the community that your version of the script exists by linking the script on your wiki's list of scripts.

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