(I created this because I want to reference it in a comment for replacing .replace( /^\s+/, '' ); with .trimStart().)

I proposed at T395347#12037702 that we go from the ES2017 requirement we have today, directly to requiring ES2019. Two in one.

In a nut shell, this is because browsers don't implement and ship features from a given spec all at the same time. And, they can also land out of order. This creates a bit of an uneven distribution where some specs have one or two straggling browsers that, once they catch up to that one feature, the next spec has already already landed in that same browser by then. This means some years we can't move much, but to compensate, we can then move two at once in other years. This year is one of those years.

The only change in Grade A requirements for ES2018 at T395347 is raising Safari 11 to Safari 12. And that automatically takes care of ES2019 in this task as well.

In T395347#12037648, @Krinkle wrote:

[…] These are the differences in browser support based on MDN data via caniuse.com (we'll confirm this later in BrowserStack when we review and verify the proposed startup.js patch, for planning purposes we can start by assuming that MDN is correct). Cells with a dash represent no change (minimum version is less then or equal to the current feature test in startup.js). Non-empty cells represent a raising of the Modern requirements (meaning that a Grade C browser goes from receiving Modern to receiving Basic). Bolded non-empty cells represent dropping support from Grade A.

Feature/Browser	Chrome	Edge	Firefox	Safari	iOS	Android
Grade A today	Chrome 109 (2023)	Edge 109 (2023)	Firefox 109 (2023)	Safari 11.1 (2018)	iOS 11.3 (2018)	Android 6 (2015) / Chrome 106 (2022)
Modern today (startup.js)	Chrome 63	Edge 79	Firefox 58	Safari 11.1	iOS 11.2	Android 5 (2014) / Chrome 95 (2021)
ES2018 for await	-	-	-	Safari 12	iOS 12	-
ES2018 async generators	-	-	-	Safari 12	iOS 12	-
ES2018 object spread	-	-	-	-	-	-
ES2018 regexp dotAll	-	-	Firefox 78	-	-	-
ES2018 named capture groups	Chrome 64	-	Firefox 79	-	iOS 11.3	-
ES2018 Unicode character class	Chrome 64	-	Firefox 78	-	iOS 11.3	-

[…]

Change #1316985 had a related patch set uploaded (by Krinkle; author: Krinkle):

[mediawiki/core@master] ResourceLoader: Raise startup.js compatibility check to ES2019

https://gerrit.wikimedia.org/r/1316985

Change #1316987 had a related patch set uploaded (by Krinkle; author: Krinkle):

[mediawiki/extensions/CodeMirror@master] JavaScriptValidator: Raise allowance to ES2019

https://gerrit.wikimedia.org/r/1316987

Change #1316987 merged by jenkins-bot:

[mediawiki/extensions/CodeMirror@master] JavaScriptValidator: Raise allowance to ES2019

https://gerrit.wikimedia.org/r/1316987

krinkle opened https://gitlab.wikimedia.org/repos/ci-tools/libup-config/-/merge_requests/138

releases: Bump eslint-config-wikimedia to 0.32.5

jforrester updated https://gitlab.wikimedia.org/repos/ci-tools/libup-config/-/merge_requests/138

releases: Bump eslint-config-wikimedia to 0.32.5

jforrester merged https://gitlab.wikimedia.org/repos/ci-tools/libup-config/-/merge_requests/138

releases: Bump eslint-config-wikimedia to 0.32.5

Change #1316985 merged by jenkins-bot:

[mediawiki/core@master] ResourceLoader: Raise startup.js compatibility check to ES2019

https://gerrit.wikimedia.org/r/1316985

In T395347#12179109, @Krinkle wrote:

Doc updates:

• https://www.mediawiki.org/w/index.php?title=Compatibility&diff=8540290&oldid=8527134
• https://www.mediawiki.org/w/index.php?title=Template%3ACompatibility_browser&diff=8540292&oldid=8482458

This shipped in wmf.14 (i.e. this week). We ideally should have announced it last week, but oh well.

I added the following to https://meta.wikimedia.org/wiki/Tech/News/2026/33:

Gadgets and scripts on Wikimedia wikis may now use ES2018 features and ES2019 features in JavaScript code. Previously, the platform only allowed up to ES2017. MediaWiki validates the source code to protect functionality from syntax errors and to ensure scripts are valid in all supported browsers.

Related previous announcements:

https://meta.wikimedia.org/wiki/Tech/News/2025/23

From this week, Wikimedia wikis will allow ES2017 features in JavaScript code for official code, gadgets, and user scripts. The most visible feature of ES2017 is async/await syntax, allowing for easier-to-read code. Until this week, the platform only allowed up to ES2016, and a few months before that, up to ES2015.

https://meta.wikimedia.org/wiki/Tech/News/2024/03

Gadgets and personal user scripts may now use JavaScript syntax introduced in ES6 (also known as "ES2015") and ES7 ("ES2016"). MediaWiki validates the source code to protect other site functionality from syntax errors, and to ensure scripts are valid in all supported browsers.

I left out mention of notable features this time, because the this year we don't have any that I think are well-known or recognisable to most Tech News subscribers. This information is linked to the "ES2018" and "ES2019" words instead.

Like last year, I left out mention of affected browsers because:

• the affected browsers (iOS 11 and Safari 11) continue to receive Basic support. This change only affects interactive features that are involve Modern JavaScript. This means readers are unaffected and there is no need to pass on a message to wider communities.
• the affected iOS device (2013 iPhone) is compatible with iOS 12, and continues to be supported with Modern JS if they upgrade,
• the only affected Mac devices (2007-2008 models) make up less than <0.1% in their combined Safari 11 usage, and those Mac devices continue to be supported with Modern JS through Firefox or Chrome.

This is so narrow that it gives undue weight to highlight directly. The linked supported browsers does provide this information to anyone curious or in need of guideance. For example it says iPhone 5s (2013) must use iOS 12, and OS X 10.11 must use Firefox or Chrome instead of Safari.

@Krinkle well noted, thanks for breakdown.

I left it open because it was the primary link in the Tech News announcement last week. Now that the week has passed, and no comments were left here, it can be resolved indeed. Thanks.