@Catrope @Krinkle, for ES6 modules/grade A experience do we test for browser support for NodeList.prototype.forEach ?
If not, do you think we should?

I can replicate this on browser stack Windows 7 Chrome 42 with the following steps:

• Log in
• Click preferences
• See error.

(confirms my suspicion about the above line)

Change 752731 had a related patch set uploaded (by Nray; author: Nray):

[mediawiki/skins/Vector@master] Fix TypeError: document.querySelectorAll(...).forEach is not a function

https://gerrit.wikimedia.org/r/752731

Change 752731 merged by jenkins-bot:

[mediawiki/skins/Vector@master] Fix TypeError: document.querySelectorAll(...).forEach is not a function

https://gerrit.wikimedia.org/r/752731

Change 752741 had a related patch set uploaded (by Nray; author: Nray):

[mediawiki/skins/Vector@master] Fix StickyHeader TypeError: document.querySelectorAll(...).forEach is not a function

https://gerrit.wikimedia.org/r/752741

Change 752766 had a related patch set uploaded (by Nray; author: Nray):

[mediawiki/skins/Vector@wmf/1.38.0-wmf.16] Fix TypeError: document.querySelectorAll(...).forEach is not a function

https://gerrit.wikimedia.org/r/752766

Change 752741 abandoned by Nray:

[mediawiki/skins/Vector@master] Fix StickyHeader TypeError: document.querySelectorAll(...).forEach is not a function

Reason:

Not needed

https://gerrit.wikimedia.org/r/752741

Change 752766 merged by jenkins-bot:

[mediawiki/skins/Vector@wmf/1.38.0-wmf.16] Fix TypeError: document.querySelectorAll(...).forEach is not a function

https://gerrit.wikimedia.org/r/752766

Mentioned in SAL (#wikimedia-operations) [2022-01-11T00:24:29Z] <urbanecm@deploy1002> Synchronized php-1.38.0-wmf.16/skins/Vector/resources/skins.vector.js/dropdownMenus.js: 79b33f2: Fix TypeError: document.querySelectorAll(...).forEach is not a function (T298910) (duration: 00m 59s)

In T298910#7610432, @Jdlrobson wrote:

@Catrope @Krinkle, for ES6 modules/grade A experience do we test for browser support for NodeList.prototype.forEach ?
If not, do you think we should?

Not explicitly, no. Here's what we check for:

• Native promise support (Promise is a function, and Promise.prototype.finally exists)
• RegExp.prototype.flags exists
• Non-BMP variable names work (var 𐋀; executes without a parse error, where 𐋀 is U+102C0 CARIAN LETTER G)

The logic here is that native promise support is a pretty good proxy for the ES6 support we need, except that a few browsers support promises but not most of the other ES6 features. The other two checks serve to filter out those browsers (Edge 17 and 18 fail the RegExp check, Safari and iOS below 14 fail the non-BMP variable names check, and Android 4.4.4 and below fail both).

Looking at caniuse for NodeList forEach, it seems to me that all browsers that pass these checks also support NodeList forEach, so I don't think it's necessary to add a check for it.

Looking at caniuse for NodeList forEach, it seems to me that all browsers that pass these checks also support NodeList forEach, so I don't think it's necessary to add a check for it.

Evidently, Chrome/49 doesn't pass these checks given the existence of this error.

• ES5 (Array.forEach) Chrome 23 https://caniuse.com/es5
• Promise available from Chrome 33 https://caniuse.com/promises
• NodeList.forEach from Chrome 51 https://caniuse.com/mdn-api_nodelist_foreach
• Regex flags from Chrome 49 https://caniuse.com/mdn-javascript_builtins_regexp_flags
• Not sure about NON-BPM names as not sure which table to check in caniuse

So I think we should test for this too.

I believe Chrome 49 should have failed the test, because we check for Promise.prototype.finally, which caniuse says is available from Chrome 63: https://caniuse.com/promise-finally .

In T298910#7614017, @Jdlrobson wrote:

Evidently, Chrome/49 doesn't pass these checks given the existence of this error.

Are we sure that Chrome 49 executed ES6 code here? The patch that was merged for this bug addressed a forEach call in ES5 code.

Are we sure that Chrome 49 executed ES6 code here

Sorry for the confusion here. No it was ES5 code that triggered the error. I'm requesting we drop it from grade A support. Maybe we should continue this conversation over at T298911 which will probably be less confusing.