Looks like this is the sort of data export that really belongs with a specific module that needs it, rather than side-wide or on every page.
```lang=json
"wgMonthNamesShort": ["", "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"],
```
However, checking Codesearch shows it isn't actually used anywhere in core, nor in any WMF-deployed extensions. And in other repos, there's also only very few uses:
* SemanticMediaWiki: 1 use of wgMonthNames in ext.smw.dataItem.time.js.
* SemanticResultFormats: 1 use of wgMonthNames in ext.srf.api.results.js
* PageForms: 1 use of wgMonthNamesShort in PF_jsGrid.js.
### Migration
For a MediaWiki extension:
* To access month names in the current user's interface language, use `mediawiki.language.months`. [Documentation: mediawiki.language](https://doc.wikimedia.org/mediawiki-core/master/js/#!/api/mw.language-property-months), and T219340#5060585 for example code
* The access month names in the wiki's main content language, you will have to either lazy-load them from the [Messages API](https://www.mediawiki.org/wiki/API:Allmessages), or (for greater performance) export them server-side in a [generated package file](https://www.mediawiki.org/wiki/ResourceLoader/Package_modules#Generated_content) where you export the result of `$context->msg('jan')->inContentLanguage()->text()` etc.
For a gadget, or user script:
* To access month names in specific language only, it might be easiest to simply declare the array in the code itself. ([example diff English](https://en.wikipedia.org/w/index.php?title=User:K175/common.js&diff=prev&oldid=945394516), [example diff German](https://de.wikipedia.org/w/index.php?title=Benutzer:Fomafix/monobook.js&diff=prev&oldid=197738132)).
* To access month names in the current user's interface language, use `mediawiki.language.months`. [Documentation: mediawiki.language](https://doc.wikimedia.org/mediawiki-core/master/js/#!/api/mw.language-property-months), and T219340#5060585 for example code.
* To access month names in the wiki's main content language, you will have to either lazy-load them from the [Messages API](https://www.mediawiki.org/wiki/API:Allmessages).