I was updating some of my JS scripts on my wiki when I noticed that the ResourceLoader did not accept some of my inputs because it's still using ECMAScript 5 (ES5), returning JavaScript parse error (scripts need to be valid ECMAScript 5): Parse error: Illegal token in file 'MediaWiki:Common.js' on line X (X being any number).
Since the upgrade to 1.36, MediaWiki now has a built-in support for ECMAScript 6 (ES6), which is essentially the default JavaScript standard nowadays, used by >90% of websites. However it seems that this is still not enabled on Miraheze yet.
I did found some specific things with "ES6" on the name in Resources.php, but I'm not sure if it's related to this.
Would be possible to enable this on wikis? Is there any complications? It's a bit though to use ES5 nowadays, as it is essentially legacy technology (mostly for IE 9, 10 and 11 support).
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