Through time the core JavaScript functions and HTML output improves functionality, introduces new methods, deprecates or changes in other aspects. This document intends to highlight the most common problems that need to be fixed.

For an overview of what is currently available in ResourceLoader, check out ResourceLoader/Modules.
Problems with gadgets? Check if it's listed below. If so, ask a sysop to update it on your wiki.
You can help with the migration on Wikimedia projects. See the 2011 Resource Walker, which also has useful tools to ease migration.

MediaWiki 1.31[edit]

Internet Explorer 10 browser[edit]

With this version, we have stopped JavaScript support for IE10. See Compatibility for details.

MediaWiki 1.29[edit]

Legacy removals[edit]

Javascript functions and variables part of wikibits.js that had been deprecated since MediaWiki 1.17 or 1.18 have been removed:

User-Agent variables: is_gecko, is_chrome_mac, is_chrome, webkit_version, is_safari_win, is_safari, webkit_match, is_ff2, ff2_bugs, is_ff2_win, is_ff2_x11, opera95_bugs, opera7_bugs, opera6_bugs, is_opera_95, is_opera_preseven, is_opera, ie6_bugs, clientPC.

DOM manipulation: changeText, killEvt, addHandler, hookEvent, addClickHandler, removeHandler, getElementsByClassName, getInnerText.

Utilities: setupCheckboxShiftClick, addCheckboxClickHandlers, mwEditButtons, mwCustomEditButtons, injectSpinner, removeSpinner, escapeQuotes, escapeQuotesHTML, jsMsg, addPortletLink, appendCSS, tooltipAccessKeyPrefix, tooltipAccessKeyRegexp, updateTooltipAccessKeys.

How to migrate[edit]

Below is a table containing migration information for the wikibits functionality. Many of the replacements are part of the mediawiki.util module, which is not loaded by default. Please declare your dependency on this module if you refer to mw.util, as described in the development guide.

Identifier	Type	Replaced by
clientPC	string	» `navigator.userAgent`
is_gecko	boolean	» jQuery.client
is_safari	boolean
is_safari_win	boolean
is_chrome	boolean
is_chrome_mac	boolean
is_ff2	boolean
is_ff2_win	boolean
is_ff2_x11	boolean
webkit_match	object
ff2_bugs	boolean	obsolete
ie6_bugs	boolean	obsolete
doneOnloadHook	boolean	» mw.hook » jQuery Use $( function( $ ) { /* your inline code to be executed after the page is loaded / } ); // or: $( LoadMyApp ); Or shorthand: jQuery( function( $ ) { / your inline code to be executed after the page is loaded */ } ); // or: $( LoadMyApp );
onloadFuncts	object
addOnloadHook	function
runOnloadHook	function
killEvt	function	» jQuery.Event: /** * @param e {jQuery.Event} Cross-browser compatible/normalized event object / $( '#mw-fooBar' ).click( function( e ) { e.preventDefault(); / do something else */ } );
loadedScripts	object	redundant
importScript	function	‎ » mw.loader // Full script url mw.loader.load( 'https://www.mediawiki.org/w/index.php?title=MediaWiki:Gadget-UTCLiveClock.js&action=raw&ctype=text/javascript' ); // Local script url mw.loader.load( '/w/index.php?title=MediaWiki:Gadget-HotCat.js&action=raw&ctype=text/javascript' ); // Full stylesheet url mw.loader.load( 'https://www.mediawiki.org/w/index.php?title=User:Example/custom-foo.css&action=raw&ctype=text/css', 'text/css' ); // Local stylesheet mw.loader.load( '/w/index.php?title=User:Example/custom-foo.css&action=raw&ctype=text/css', 'text/css' );
importStylesheet	function
importScriptURI	function
importStylesheetURI	function
appendCSS	function	» mw.util.addCSS
addHandler	function	» jQuery Events Using `.on()` one can add event handlers. Some of the more common events have their own shortcuts (such as `.click()`). // Attach multiple events to an element and attach an anonymous function $( '#fooBar' ).on( 'mouseenter mouseleave', function() { alert( '#fooBar is moused!' ); } ); // Attach multiple events with different handlers to a single element $( '#fooBar' ).on( { click: function() { // do something on click }, mouseenter: function() { // do something on mouseenter } } ); // Attach a handler to the click events of an earlier defined DOM element $( myElement ).click( myFunction );
addClickHandler	function
removeHandler	function
hookEvent	function
mwEditButtons	object	obsolete
mwCustomEditButtons	object	» WikiEditor The new WikiEditor (which also works fine in Monobook, see here) has built-in function to customize the toolbar. For more info see Extension:WikiEditor/Toolbar customization. For examples to insert buttons using the native script see Extension:WikiEditor/Toolbar customization/Library. For a script to insert buttons using a simple syntax similar to the old way check out meta:User:Krinkle/Scripts/insertVectorButtons#Description mw.loader.load( '//meta.wikimedia.org/w/index.php?title=User:Krinkle/insertVectorButtons.js' + '&action=raw&ctype=text/javascript' ); function kCustomMainInsertButton_config(){ // {{Welcome}} ~~~~ kCustomMainInsertButton( 'welcome', // Id '//commons.wikimedia.org/w/thumb.php?f=Nuvola_apps_edu_languages.svg&w=22', // File 'Welcome', // tooltip '{\{Welcome}\}\~\~\~\~', // Open tag '', // Close tag '' // sampleText ); // {{subst:Test2}} ~~~~ kCustomMainInsertButton( 'test2', // Id '//commons.wikimedia.org/w/thumb.php?f=Nuvola_apps_important.svg&w=22', // File 'Test2', // tooltip '{\{subst:test2\|', // Open tag '}\}\~\~\~\~', // Close tag '' // sample text ); }
tooltipAccessKeyPrefix	string	» jquery.accessKeyLabel // myElement.accessKey = 'x'; // myElement.title = 'Example [x]'; mw.loader.using('jquery.accessKeyLabel').then(function () { $(myElement).updateTooltipAccessKeys(); });
tooltipAccessKeyRegexp	object
updateTooltipAccessKeys	function
ta	object	MediaWiki:Accesskey-* and MediaWiki:Tooltip-*.
akeytt	function	obsolete
checkboxes	object	» jquery.checkboxShiftClick
lastCheckbox	object
setupCheckboxShiftClick	function
addCheckboxClickHandlers	function
checkboxClickHandler	function
showTocToggle	function
toggleToc	function
ts_image_path	string	» jquery.tablesorter
ts_image_up	string
ts_image_down	string
ts_image_none	string
ts_europeandate	boolean
ts_alternate_row_colors	boolean
ts_number_transform_table	object
ts_number_regex	object
sortables_init	function
ts_makeSortable	function
ts_getInnerText	function
ts_resortTable	function
ts_initTransformTable	function
ts_toLowerCase	function
ts_dateToSortKey	function
ts_parseFloat	function
ts_currencyToSortKey	function
ts_sort_generic	function
ts_alternate	function
changeText	function	» jQuery Using `.text()` one can get (or set) the text content of an element: // Set text of an earlier defined element $( myElement ).text( 'New text!' ); // Set text for multiple elements at once $( '.mw-userlink' ).text( 'Mr. Foobar' ); // Get the text of an element $( myElement ).text();
getInnerText	function
escapeQuotes	function
escapeQuotesHTML	function	» mw.html
addPortletLink	function	» mw.util.addPortletLink
jsMsg	function	» mw.util.jsMessage
injectSpinner	function	» jquery.spinner (Documentation) jQuery( .. ).injectSpinner('some-id'); jQuery.removeSpinner('some-id');
removeSpinner	function
getElementsByClassName	function	» jQuery Use the CSS Selector in jQuery to select elements by classname. Here examples for the three most common usecases of `getElementsByClassName()`: // Get everything with a classname $( '.myclass' ); // Get all of element X (ie. table) with a classname $( 'table.wikitable' ); // Get all of something within another element $( myDomElement ).find( '.myclass' ); $( myDomElement ).find( '> .myclass' ); // only direct children // Get all class-elements that are direct children of an element $( '#someElement .myclass' ); $( '#someElement > .myclass' ); // only direct children
redirectToFragment	function

Internet Explorer 9 and pre-ES5 browsers[edit]

With this version, we have stopped JavaScript support for IE9 and other browsers that do not support ES5. See Compatibility for details.

Gadget type[edit]

Background[edit]

Since early 2011, gadgets with styles (both "only styles" and "styles and scripts") had their styles loaded twice. T42284 and https://gerrit.wikimedia.org/r/308096 address this bug.

What's new[edit]

This bug was addressed by adding support in the Gadgets extension for the ResourceLoader "type" feature. This allows gadget developers to configure how the module should be loaded

type=styles: Load module styles via <link rel="stylesheet">. (Loads early, applies styles before skin and page are ready, also works when JavaScript is disabled.)
type=general: Load module scripts and/or styles via mw.loader.load(). (Applies styles after the skin and page are ready, right before JS execution, has better caching.)

Gadgets with only styles, internally get type=styles by default. Gadgets with only scripts default to type=general.

Gadgets with both scripts and styles currently default to loading both ways (just before the bug was fixed). When this happens, a warning is shown in the console that asks the developer to provide the desired type.

Once we've given gadget developers enough time to migrate, we can make type=general the default for gadgets that have both scripts and styles.

How to migrate[edit]

Gadget "mygadget" styles loaded twice. Migrate to type=general. See https://phabricator.wikimedia.org/T42284.

If you see this warning, that means your gadget contains both scripts and styles. Here are two ways to fix the warning:

If the styles in your gadget are there to provide styling for things created by the gadget, add "type=general" to your gadget definition ("MediaWiki:Gadgets-definition").
Or – If the styles in your gadget are there to provide styling for things that are part of the skin or on the page, then these styles should not be together with the scripts in the same gadget. Convert the gadget to two separate gadgets. One gadget that is styles-only, and the other with the scripts. If the scripts gadget also has its own styles, then also set "type=general" on the original gadget (per point 1). If you want to keep presenting the modules as one gadget on the Preferences page, use #Gadget peers.

As you can see, in most cases the solution is "type=general." And in the future, this will become the default and we will not load styles twice. Right now, loading twice remains the default for compatibility with older gadgets covered by point 2 above. Changing these mixed gadgets to type=general now would cause some styles to load too late and cause a "flash of unstyled content".

Gadget peers[edit]

For a long time, gadget authors have been interested in being able to provide a visual enhancement for all pages and also accompanying some scripting logic to apply related changes to interactive interfaces created by other modules. This requires the gadget to have both scripts and styles, but most of the styles are not required by the scripts – rather, the styles should apply directly to the page without waiting for JavaScript. So far this required either creating two gadgets (and requiring users to enable both), or creating a single gadget with the downside of the styles applying slightly after the page loads.

To accommodate the use case of a single gadget providing both page styles (which don't depend on JavaScript) and JavaScript code with its own styles, a new setting was introduced: peers. This is similar to dependencies, except that where dependencies load before the main module (not before the page itself), peers will allow one to reference a separate gadget module that will be loaded regardless of whether JavaScript is enabled.

For example:

* example [ResourceLoader|dependencies=mediawiki.util|peers=example-pagestyles] | example.js | example.css
* example-pagestyles [hidden] | example-pagestyles.css

This will register a gadget named "Example" in the preferences which, if enabled, will load example-pagestyles before the page renders. And, once JavaScript is available, the example module will also be loaded with its own dependencies, styles and scripts.

MediaWiki 1.27[edit]

Legacy default: mediawiki.util[edit]

The $wgPreloadJavaScriptMwUtil option was removed. This option allowed third-party MediaWiki administrators to re-enable the unconditional preload of mediawiki.util by default for all users (for backwards compatibility). It was disabled by default since MediaWiki 1.26, and has been disabled on Wikimedia wikis since 2014. Extensions, skins, gadgets and scripts that use the mediawiki.util module must express a dependency on it.

bits.wikimedia.org[edit]

The internal Wikimedia domain "bits.wikimedia.org" was deprecated sometime mid-2015. The following common paths should be migrated to avoid breakage once the domain is decommissioned (T107430).

bits.wikimedia.org/:domain/load.php → https://:domain/w/load.php . Moved back to local domains, alongside /w/index.php and others.
bits.wikimedia.org/static-current/* → https://:domain/static/current/: Moved to local domain, sharing a hostname-agonistic Varnish cache.
- bits.wikimedia.org/skins/* → https://:domain/static/current/skins
bits.wikimedia.org/static-1.xx-wmf.X/* → https://:domain/w/*: Specific versions can now be accessed through the regular script path. Wikimedia's multiversion entry point automatically serves the the file from to the wikis' current MediaWiki version. (T99096)
- bits.wikimedia.org/static-1.xx/skins/* → https://:domain/w/skins/*
- bits.wikimedia.org/static-1.xx/extensions/* → https://:domain/w/extensions/*
- bits.wikimedia.org/static-1.xx/resources/* → https://:domain/w/resources/*

Internet Explorer 8[edit]

Following the deactivation of JavaScript in Internet Explorer 6 and 7 in MediaWiki 1.24, JavaScript has been deactivated in Internet Explorer 8. See Compatibility for details.

MediaWiki 1.26[edit]

Legacy gadgets[edit]

Gadgets are now required to use ResourceLoader. For many Gadgets, migrating to ResourceLoader will be as easy as adding [ResourceLoader] to its definition on MediaWiki:Gadgets-definition. If after adding that, the gadget is not working properly, consult the rest of this page to look for functionality that may have been removed since the gadget was last maintained. If you run into any issues or find features that don't work without a clear way of making it work, please reach out to MediaWiki developers and fellow gadget authors on the talk page, via IRC, or on the wikitech-l mailing list.

Global variables are not global[edit]

When ResourceLoader loads a gadget script, it is not executed in global context. This means that local variables you define in the script are actually local, and not assumed to be also global. They are local to the function your code is wrapped in. It's best to modularize your code to avoid using globals, see "Globals" in MediaWiki's JavaScript coding conventions. However, if you need to export a variable to the global scope, you can explicitly assign them as window properties. For example:

// This is a local variable
var foo;
// This is a local function
function bar() {
 ..
}

// This is a global variable (accessible from other scripts, and from legacy event handlers, e.g. onclick="javascript:Quux();"
window.Quux = function( width, height ) {
	...
};

Code within your gadget can access foo and bar. Code outside the gadget (or code evaluated as separate programs, such as legacy onclick handlers), can only access Quux..

As of August 2015, ResourceLoader debug mode still executes scripts in global scope (phab:T64605), so your code may seem to work fine in debug mode but be broken in regular mode.

Font mw-geshi[edit]

The font-size of <syntaxhighlight> was often too small by default due to a font-family CSS bug. This was fixed in MediaWiki 1.26 (see (phab:T28204).

The mw-geshi, source-css, source-javascript and related classes no longer exist. Related code such as the following can be safely removed:

/* Fix <syntaxhighlight> text size. [[phab:T28204]] */
div.mw-geshi div,
div.mw-geshi div pre,
span.mw-geshi,
pre.source-css,
pre.source-javascript,
pre.source-lua {
    font-family: monospace, Courier !important;
}

Inline scripts[edit]

To inject JavaScript inline, use ResourceLoader::makeInlineScript() to wrap the JavaScript code in an anonymous function that can access MediaWiki-related objects properly, and OutputPage::addScript() to add the results to the page source for execution.

For example:

$outputPage = RequestContext::getMain()->getOutput();

$js = 'alert("hello world");';
$wrappedJS = ResourceLoader::makeInlineScript($js);
$outputPage->addScript($wrappedScript);

MediaWiki 1.24[edit]

Internet Explorer[edit]

Browser support for Internet Explorer 6 and 7 changed from Grade A to Grade C. This means JavaScript is no longer executed in these browser versions. See Compatibility for details.

MediaWiki 1.20[edit]

New diff styles[edit]

This version introduces a new diff view, greatly improved in clarity especially for whitespace and other small changes and colour-blind users. If your wiki has custom CSS for the diffs, they may be in conflict with the new style (as happened on ptwiki and srwiki). You are recommended to remove the old code (or if still wanted by some users, update it to work with the new layout and create a gadget for it so that users can opt-in to it still).

MediaWiki 1.19[edit]

wikitable style updates[edit]

As of MediaWiki 1.19 a few bugs have been fixed with the wikitable class (see phab:T32485 and phab:T35434 for more info). If your wiki maintains a legacy synonym of this class (e.g. "prettytable") you need to update its CSS to match the current style in core.

The current style as of 1.19 can be found here. Copy those rules to your wiki and replace "wikitable" with the synonym (example for nl.wikipedia).

If your wiki doesn't keep something like this, then no update is necessary and everything should take care of itself.

File page checkered background[edit]

Checkered background

The checkered background often applied to transparent file namespace pages is now part of the software. Local rules like the following should be removed (because they are redundant, and actually cause an additional unnecessary HTTP request for the image)

/* Put a checker background at the image description page.
   Only visible if the image has transparent background.
*/
#file img {
	background: url("//upload.wikimedia.org/wikipedia/commons/5/5d/Checker-16x16.png") repeat;
}

Trackbacks[edit]

Trackbacks were removed from MediaWiki core, so any styling targeting #mw_trackbacks can be removed.

MediaWiki 1.18[edit]

Protocol-relative urls[edit]

This change only applies to Wikimedia Foundation wikis.

As of MediaWiki 1.18 there is native support for protocol-relative wiki installations. This means that a wiki could be accessible from both http://example.org/ and https://example.org./ To make it possible to a share a common cache for as much as possible, we make use of a technique called protocol-relative urls. Although browsers have supports this for ages, script writers generally aren't very familiar with it until fairly recently. Briefly explained, this means that <img src="//meta.wikimedia.org" /> when on "https://example.org" will be automatically expanded by the browser to https://meta.wikimedia.org./ This is much like (for example) <img src="foobar.jpg" /> or <img src="/w/foobar.jpg" />, which are are automatically expanded to "http://mediawiki.org/w/foobar.jpg".

Depending on how the scripts were written this may require some changes to be made to your scripts. If you use the following method to detect whether the script is executed on a certain wiki, this change will break your script:

if ( wgServer === 'http://en.wikipedia.org' ) {
	// Doesn't work anymore!
}

because wgServer is now "//en.wikipedia.org". For a few years there has been another config variable, called "wgDBname". You should use that instead to differentiate wikis, like:

if ( mw.config.get( 'wgDBname' ) === 'enwiki' ) {
	// English Wikipedia!
}

Alternatively, you can use wgServerName which is without the protocol or port:

if ( mw.config.get( 'wgServerName' ) === 'en.wikipedia.org' ) {
	// English Wikipedia!
}

"Enabled by default" (Gadgets extension)[edit]

As of the version of the Gadgets extension at the MW 1.18 branchpoint, there is a new feature that allows a gadget to be opt-out instead of opt-in based. By setting "[default]" (or adding "|default" to an existing section) the gadget will be enabled by default for everybody, unless a user has specifically opted out by unticking the checkbox on Special:Preferences#mw-prefsection-gadgets.

Note that this also loads it for all anonymous users. Gadgets that are only for logged-in users should be additionally restricted by, for example, requiring certain user rights.

mw.util.wikiScript[edit]

The actual paths have not changed, but getting the path to the API and index.php has become a lot easier. This also makes the code more portable as it has no hardcoded wiki-specific paths.

This is how it used to go in many gadgets.

var foo = 'bar';
var apiUrl = '//www.mediawiki.org/w/api.php?foo=' + encodeURIComponent( foo ) + '&baz=quux';

$.ajax( { url: apiUrl, ... } );

Instead use something like one of the following:

// Behold, mw.util.wikiScript!
var foo = 'bar';
var apiUrl = mw.util.wikiScript( 'api' ) + '?foo=' + encodeURIComponent( foo ) + '&baz=quux';

$.ajax( {
	url: apiUrl,
	...
} );

You may also want to use $.param to automatically escape and create things properly in the query string:

// $.param is also awesome. No need for encodeURIComponent that way :)
var foo = 'bar';
var apiUrl = mw.util.wikiScript( 'api' ) + '?' + $.param( {
	foo: foo,
	baz: 'quux'
} );

$.ajax( {
	url: apiUrl,
	...
} );

You can even use the data option of $.ajax, that abstracts away the need to deal with the query string entirely:

// No longer needed to inject the '?' or '&' in the url
$.ajax( {
	url: mw.util.wikiScript( 'api' ),
	data: {
		foo: 'bar',
		baz: 'quux'
	}, ...
} );

MediaWiki 1.17[edit]

jQuery[edit]

See also jQuery

As of 1.17 the jQuery library is loaded by default on all MediaWiki pages. Each MediaWiki release will keep it up to date with the latest version of jQuery. If you used to load jQuery from within your script, (e.g. from ajax.googleapis.com), make sure you remove that. If you load jQuery more than once on a page, it overwrites the earlier version. Other scripts break because they may not work with an older version of jQuery.

Also, by overwriting the jQuery object, any plugins that were bound to that object are also lost.

Global identifier "$j" has been deprecated. Use jQuery or $ instead.

Tabs (vector)[edit]

In 1.17 the HTML construction for the navigation tabs has changed from <li><a><span /></a></li> to <li><span><a /></span></li>. The most common situation in which this causes problems is where scripts assume the presence of the span element when, for example, customizing the tab for "Main Page". Before 1.17 this usually meant that wikis had a different implementation for Monobook and one for Vector (or only one for each and the other was distorted).

Please use MediaWiki:Mainpage-nstab or refer to Snippets/Main Page tab for a script that will work in both Vector and Monobook for 1.17.

Adding portlet links[edit]

The legacy function addPortletLink has been rewritten as mw.util.addPortletLink. The syntax and argument order is fully backwards compatible. The differences

Support for all core skins now
Support for simple id-selector as 'nextNode' (see documentation for details).

Some wikis may have re-defined / overwritten the addPortlinkLink function to support a few extra skins. This is no longer needed. The function definition should be removed and calls adjusted to mw.util.addPortletLink.

The legacy version of addPortlinkLink has been preserved as-is in case some edge cases would behave differently (for that reason the addPortlinkLink does not redirect to mw.util.addPortlinkLink)

Toolbar[edit]

The legacy array mwCustomEditButtons has been refactored into the mw.toolbar library. The global array still exists in wikibits to avoid fatal errors but is no longer used due to race conditions. Code may run too late when the toolbar already exists. Using mw.toolbar.addButton will work always, even if the toolbar has already been created.

See mw.toolbar Documentation.

Note that mw.toolbar, just like the old mwCustomEditButtons array, are associated with the classic toolbar. The current default wikitext editor is WikiEditor, which has its own API. See Extension:WikiEditor/Toolbar customization for more information.

Sajax[edit]

The legacy functions such as sajax_init_object have been deprecated. Instead, mw.Api from the mediawiki.api module, or jQuery.ajax.

Migration guide:

标识符	类型	替换为
sajax_debug_mode	string	» jQuery.ajax Use `AJAX` functions to access pages and the API directly. $( '#mybox' ).load( '/wiki/Template:ResourceLoader_navigation #bodyContent' ); $.get( mw.config.get( 'wgScript' ), { title: 'ResourceLoader', action: 'raw' }, function( data ) { /* Call was successful do something with "data" / } ); $.getJSON( mw.util.wikiScript( 'api' ), { format: 'json', action: 'query', titles: 'Main Page', prop: 'info' }, function( obj ) { / API call was successful do something with obj */ } ); For more information see documentation for .load(), .get(), .getJSON() and the other jQuery Ajax functions. See also this guide from WikiProject User scripts, for an example of how to edit a wikipage using AJAX.
sajax_request_type	string
sajax_debug	function
sajax_init_object	function
wfSupportsAjax	function
sajax_do_call	function	$.get( mw.util.wikiScript(), { action: 'ajax', rs: 'SomeExtensionFunction', rsargs: [arg1, arg2, arg3] // becomes &rsargs[]=arg1&rsargs[]=arg2... } ); Note: These calls using action=ajax should be rewritten to use an API module

Client testing[edit]

Checking which browser, platform, layout engine etc. has should now be done with jQuery.client.

is_safari, is_chrome etc. are deprecated
No need to navigator.userAgent.indexOf("MSIE 6")==-1 etc.

Sysop script[edit]

New in MediaWiki 1.17 is a user groups module that can automatically load scripts and styles from the MediaWiki namespace for a particular user group. For example, if the wiki has MediaWiki:Group-sysop.js, this script is automatically loaded for all users in that group.

This should obsolete customisations wikis may have with regards to loading MediaWiki:Sysop.js with importScript inside Common.js.

mw.loader[edit]

If you need certain scripts like jQuery UI's dialog or datepicker, instead of doing something like:

importStylesheetURI( mw.config.get( 'wgExtensionAssetsPath' ) + '/Example/css/jquery-ui-1.7.2.css' );

$.getScript( mw.config.get( 'wgExtensionAssetsPath' ) + '/Example/js/jui.combined.min.js', function () {
	MyTool.init();
} );

Instead use this:

mw.loader.using( ['jquery.ui.dialog', 'jquery.ui.datepicker'], MyTool.init );

Or if you need to delay initialization until document.ready:

mw.loader.using( ['jquery.ui.dialog', 'jquery.ui.datepicker'], function () {
	$( document ).ready( MyTool.init );
} );

Migrating user scripts[edit]

Contrary to importScriptURI, Wikibits.js functions such as importScript() tend to be widespread among user script. Larger wikis may want to implement their own importScript function in MediaWiki:Common.js to make migration simpler. MediaWiki:Common.js is loaded as part of the "site" module which is guaranteed to load before the "user" module.

Dependencies[edit]

When a script depends on another module, such as oojs or mediawiki.util, you will need to declare this as a "dependency". This is because modules are loaded on-demand and asynchronously (in consecutive order: all at the same time), so a script needs to make sure a module has been loaded before it can use its methods. On-site modules, like gadgets, have a registry to declare these dependencies. For user scripts, one has to wrap code with mw.loader.using().

While this has been required since 2011, many scripts have continued to work without declaring their dependencies. Scripts may have worked before by accident as long as at least one user script (that used the same methods) did declare their dependencies and happened to load earlier.

With MediaWiki 1.19, page view performance has been optimised to use fewer modules by default. This makes it increasingly more important to declare the dependencies. Otherwise, your script may fail because any of the 1000+ modules you might refer to in your code would not be loaded yet. Loading everything all the time would be much too slow.

The only two base modules that are always present are mediawiki and jquery.

In practice[edit]

Use mw.loader.using() to declare any modules that you need before executing the contents of "function". You can pass multiple modules as an array of strings.

mw.loader.using( ['mediawiki.util', 'oojs', 'jquery.cookie'], function () {

	/* some other script that uses $.cookie */

	/* some other script that uses mw.util and OO.EventEmitter() */

} );

Global wg variables[edit]

As of MediaWiki 1.17, the global config variables are deprecated. Rationale to clear the global namespace, working towards a reality where most of the core libraries will be object oriented as part of the mw object. Configuration is managed through an instance of mw.Map in mw.config. It is also supporting the behaviour of more script executing in their own local/private scope as opposed to the global scope.

Legacy globals will be kept for backwards compatibly, but people should start migrating so that they may removed in a future version of MediaWiki (task T35837).

if ( mw.config.exists( 'wgGlobalGroups' ) {
	// do stuff
}

if ( mw.config.get( 'wgCanonicalSpecialPageName' ) === 'Search' ) {
	// do stuff
}

// Retrieve multiple variables for concise repeated access
var conf = mw.config.get( [
	'wgPageName',
	'wgAction'
] );
if ( conf.wgAction === 'view' ) {
	// do stuff
}

More info: ResourceLoader/Default modules#mw.config

Ready, onload, hook[edit]

Check JavaScript deprecation overview for "addOnloadHook". Use $( function ); instead, or $( fn ); for short.

New CSS declarations in core[edit]

Headings overflow hidden[edit]

overflow:hidden for any of h1, h2, h3, h4, h5 and/or h6 can be safely removed from stylesheets as this is now part of the core.

Italic redirects[edit]

Links to redirects appear italicized on Special:AllPages, Special:PrefixIndex, Special:Watchlist/edit and in category listings

.allpagesredirect,
.redirect-in-category,
.watchlistredir {
 font-style: italic;
}

wpSummary[edit]

Per phab:T22276, input#wpSummary's width is now set in Vector as well (instead of just Monobook).

UsabilityInitiative no more[edit]

As of 1.17 the functionality developed by the UsabilityInitiative has been extracted to stand-alone extensions. Buttons like "#pt-optin-try" no longer exist. You can enable/disable these functions like other extensions via Special:Preferences.

Scripts and styles doing things like "HideUsabilityOptIn":

#pt-optin-try {
	display: none !important;
}

should therefore be deleted entirely as the button no longer exists.

Preformatted JS/CSS pages[edit]

It's no longer useful to wrap these pages in /* <pre> */ or // <source lang="javascript"> etc. In newer versions of MediaWiki, these pages are rendered as code automatically (including syntax highlighting when available). See also task T6801.

Table sorter[edit]

The old table sorter in wikibits.js was removed in favour of jquery.tablesorter.

Variables such as ts_alternate_row_colors, and functions like ts_parseFloat and ts_dateToSortKey no longer exist.

MediaWiki 1.16 and before[edit]

importScript[edit]

As of 2008, the function importScript is part of MediaWiki. Wikis that have defined this function themselves may remove that. It will automatically use the new function. This also goes for importStylesheet, importStylesheetURI and importScriptURI.

Make sure that before removing such local function though that the function signature is compatible with the core function and that there are no additional locally implemented arguments or features that core doesn't have (or vice versa). When in doubt, either keep it untouched or replace the function body with a compatibility call to the new core functionality (thus re-routing it instead of removing it entirely).

importScriptURI has been deprecated in favor of using jQuery directly. Use $.getScript instead of importScriptURI.

addPortletLink[edit]

As of 2008, the function addPortletLink is part of MediaWiki. Many wikis and gadgets have created functions like addLink, addLiLink, addlilink etc. these should be removed as they most likely don't support different skins (ie. only Monobook, not Vector or older skins). Be sure to check the syntax as there is no way of knowing the creator of those local functions used the same parameter order.

Note: The global function was deprecated in 2012 and moved to the mediawiki.util module as mw.util.addPortletLink()

appendCSS[edit]

As of 2008, the function appendCSS is part of MediaWiki. Wikis that have defined this function themselves may remove that. It will automatically use the new function.

Note: The global function was deprecated in 2012 and moved to the mediawiki.util module as mw.util.addCSS()

HTML bugs in core[edit]

html lang[edit]

This bugfix is obsolete as MediaWiki does this correctly by default. (example)

var htmlE = document.documentElement;
htmlE.setAttribute('lang', mw.config.get('wgUserLanguage'));

CSS declarations new in core[edit]

wikitable[edit]

The .wikitable CSS class is part of MediaWiki. Wikis that previously defined this class in their Common.css should remove it. Do check if the wiki has any customisations that should be retained (e.g. different background-color, or font-size).

plainlinks[edit]

The .plainlinks CSS class is part of MediaWiki. Wikis that previously defined this class in their Common.css should remove it.

Many wikis defined this functionality under a different name: .plainlinksneverexpand. Once any usage is replaced with "plainlinks", it may also be removed. (Search with insource:plainlinksneverexpand.)

mw-plusminus[edit]

The CSS classes .mw-plusminus-pos, .mw-plusminus-null, and .mw-plusminus-neg are now implemented by MediaWiki.

External URLs[edit]

Icons for protocols like HTTP, IRC, etc. and file types like PDF are now supported by MediaWiki.

Tooltip and accesskeys[edit]

Scripts like ta['pt-userpage'] = new Array('.','My user page'); are ignored. It was deprecated in 2009. The function akeytt() no longer exists. Tooltips and accesskeys are now supported from core. The most common values that wikis used with ta[] are the same that have now been integrated into the core (ie. "." for "my user page"). They can still be modified, if really needed, by sysops in MediaWiki-messages (no need for JavaScript workarounds anymore).

As of MediaWiki 1.19 the global dummy placeholder ta = new Object(); was removed from wikibits.js. Code trying to add members to it will likely emit an exception.

Good practices[edit]

Anything not related to a particular MediaWiki version that should be noted as it is often done in a way that could or must be better.

Avoid document.write()[edit]

Do not use, will cause blank pages; instead, use jQuery to modify the document (adding elements, changing things etc.) and the import functions to load external resources. (importStylesheet, importScript, mw.loader.load, $.getScript).

Example: replace

document.write('<script type="text/javascript" src="'
             + 'http://commons.wikimedia.org/w/index.php?title=MediaWiki:Gadget-HotCat.js'
             + '&action=raw&ctype=text/javascript"></script>');

with

mw.loader.load( '//commons.wikimedia.org/w/index.php?title=MediaWiki:Gadget-HotCat.js&action=raw&ctype=text/javascript' );

Event binding[edit]

Binding events and callback functions is very tricky and it is hard to implement it in good cross-browser way that supports all browsers MediaWiki supports too.

As a good practice it is recommended to use jQuery methods for event binding. See the JavaScript deprecation overview on "addHandler" for examples on more info for this.

Encoding and escaping[edit]

When working with regexes, user input and/or urls always encode and escape!

Regexes: mw.RegExp.escape (provided by mediawiki.RegExp module)
HTML: mw.html.escape (provided by default)
URL: mw.util.rawurlencode (for normal values), mw.util.wikiUrlencode for page titles, does not escape colons (:) and slashes (/). (provided by mediawiki.util module)

Prototyping[edit]

Do not extend native JavaScript constructors with non-standard methods (e.g. String.prototype.foobar, Regex.myMethod, Array.prototype.inArray etc.). Depend on the es5-shim module to preload (in older browsers) standard polyfills for JavaScript 1.8 and ECMAScript 5 methods. See also Annotated ES5 specification and es5-shim.

// This loader() command immediate runs "done" in modern browsers,
// In older browsers it loads es5-shim.js first.
mw.loader.using( 'es5-shim').done( function () {
	console.log( '    bar    '.trim() ); // "bar"
	[ 'a', 'b' ].forEach( function ( val ) {
		/* .. */
	} );
} );

Getting URL parameter values[edit]

Functions like getURLParamValue, getParamVal, getParamValue, etc. are very common across wikis. Some are better than others (i.e. what if a parameter appears twice? (it should return the last one), does it ignore anything after the #tag?). As of 1.17 mw.util.getParamValue is available everywhere and takes these factors into account. Perform a full-text all-namespace search for these function names. If they are widely used perhaps make a note about it in the local village pump. Any site-wide scripts should be updated to use the mw.util function. If there are any serious problems with the local implementation (like not escaping the value for regex), it may be wise to redirect the function:

function getURLParamValue( p, url ) {
	return mw.util.getParamValue( p, url );
}

Avoid use of !important[edit]

CSS stands for Cascading Style Sheets. Cascading means what comes later overwrites what came earlier. In most cases there is no need to use !important. See the following example:

.my-element { color: blue; }
.my-element { color: green; }

Text inside <strong class="my-element"> will now be green.

Keep gadgets central[edit]

Gadgets that are highly used across wiki (like Gadget-LiveClock.js) should be kept central (ie. Meta-Wiki or MediaWiki.org). The following is a list of gadgets that are centrally stored and

made compatible with 1.17
work in Monobook and Vector
wiki independent (ie. can be loaded on Commons, Wikipedia, Wiktionary or John Doe's Wiki without problems)

Sysops: To update a gadget on your wiki:

Check MediaWiki:Gadgets-definition on your wiki and find the gadget in question.

The part after the pipe (|) is the scriptname (eg. "UTCLiveClock.js").

Go to MediaWiki:Gadget-<scriptname> (eg. MediaWiki:Gadget-UTCLiveClock.js)

Remove everything and replace with the code in they grey area below the scriptname in the list. For an example on how this is done, check out LiveClock on Simple Wikipedia.

Gadgets[edit]

UTCLiveClock

mw.loader.load('https://www.mediawiki.org/w/index.php?title=MediaWiki:Gadget-UTCLiveClock.js&action=raw&ctype=text/javascript');

contribsrange

mw.loader.load('https://www.mediawiki.org/w/index.php?title=MediaWiki:Gadget-contribsrange.js&action=raw&ctype=text/javascript');

modrollback

mw.loader.load('https://www.mediawiki.org/w/index.php?title=MediaWiki:Gadget-modrollback.js&action=raw&ctype=text/javascript');

QPreview

mw.loader.load('https://commons.wikimedia.org/w/index.php?title=MediaWiki:Gadget-QPreview.js&action=raw&ctype=text/javascript');

ShortDiff

mw.loader.load('https://meta.wikimedia.org/w/index.php?title=MediaWiki:Gadget-ShortDiff.js&action=raw&ctype=text/javascript');

lastdiff Check Snippets/Last revision action
HotCat

/**
 * This imports the latest version of HotCat from Commons.
 * HotCat is a gadget to make changes to categories much easier.
 * Full documentation can be found at https://commons.wikimedia.org/wiki/Help:Gadget-HotCat
 */
mw.loader.load('https://commons.wikimedia.org/w/index.php?title=MediaWiki:Gadget-HotCat.js&action=raw&ctype=text/javascript');

WikiMiniAtlas

/**
 * WikiMiniAtlas is a popup click and drag world map.
 * See [[meta:WikiMiniAtlas]] for more information.
 * Maintainers: [[w:User:Dschwen]]
 */
mw.loader.load('https://meta.wikimedia.org/w/index.php?title=MediaWiki:Wikiminiatlas.js&action=raw&ctype=text/javascript');

Navigation Popups (MediaWiki:Gadget-popups.js and MediaWiki:Gadget-popups.css respectively)

mw.loader.load('https://en.wikipedia.org/w/index.php?title=MediaWiki:Gadget-popups.js&action=raw&ctype=text/javascript');

@import url('https://en.wikipedia.org/w/index.php?title=MediaWiki:Gadget-navpop.css&action=raw&ctype=text/css');

jQuery optimization[edit]

Use API instead of index.php[edit]

XML retrieved by invoking GET and POST methods on index.php is incompatible with HTML 5, which is the default as of 1.16 (and WMF sites since 17th of September, 2012). You should update code to use api.php, JSON format and jQuery.ajax immediately. Use the ResourceLoader modules that do this for you to simplify interactng with the API, including mediawiki.api.

A temporary fix for problems with DOM parsing of XML retrieved via AJAX: For example the method getElementById("foobar") on a XML object from Mozilla's DOMParser stopped to work as before. Replacing the getElementById with $('#foobar', client.responseText).get(0) might work without many other changes to your code. Updating your script to the above mentioned methods is strongly recommended, however.

Conventions[edit]

Manual:Coding conventions/JavaScript – keep if statements with brackets, use proper indention (block B in block A is indented more, visualize the tree), etc.
Manual:Coding conventions/CSS – combine selectors, remove stuff now in core, etc.

MediaWiki 1.31[edit]

Internet Explorer 10 browser[edit]

MediaWiki 1.29[edit]

Legacy removals[edit]

How to migrate[edit]

Internet Explorer 9 and pre-ES5 browsers[edit]

Gadget type[edit]

Background[edit]

What's new[edit]

How to migrate[edit]

Gadget peers[edit]

MediaWiki 1.27[edit]

Legacy default: mediawiki.util[edit]

bits.wikimedia.org[edit]

Internet Explorer 8[edit]

MediaWiki 1.26[edit]

Legacy gadgets[edit]

Global variables are not global[edit]

Font mw-geshi[edit]

Inline scripts[edit]

MediaWiki 1.24[edit]

Internet Explorer[edit]

MediaWiki 1.20[edit]

New diff styles[edit]

MediaWiki 1.19[edit]

wikitable style updates[edit]

File page checkered background[edit]

Trackbacks[edit]

MediaWiki 1.18[edit]

Protocol-relative urls[edit]

"Enabled by default" (Gadgets extension)[edit]

mw.util.wikiScript[edit]

MediaWiki 1.17[edit]

jQuery[edit]

Tabs (vector)[edit]

Adding portlet links[edit]

Toolbar[edit]

Sajax[edit]

Client testing[edit]

Sysop script[edit]

mw.loader[edit]

Migrating user scripts[edit]

Dependencies[edit]

In practice[edit]

Global wg variables[edit]

Ready, onload, hook[edit]

New CSS declarations in core[edit]

Headings overflow hidden[edit]

Italic redirects[edit]

wpSummary[edit]

UsabilityInitiative no more[edit]

Preformatted JS/CSS pages[edit]

Table sorter[edit]

MediaWiki 1.16 and before[edit]

importScript[edit]

addPortletLink[edit]

appendCSS[edit]

HTML bugs in core[edit]

html lang[edit]

CSS declarations new in core[edit]

wikitable[edit]

plainlinks[edit]

mw-plusminus[edit]

External URLs[edit]

Tooltip and accesskeys[edit]

Good practices[edit]

Avoid document.write()[edit]

Event binding[edit]

Encoding and escaping[edit]

Prototyping[edit]

Getting URL parameter values[edit]

Avoid use of !important[edit]

Keep gadgets central[edit]

Gadgets[edit]

jQuery optimization[edit]

Use API instead of index.php[edit]

Conventions[edit]

See also[edit]