observe-sequence@1.0.18 syntax broken on IE 11

[dougfabris]

Recently we updated the meteor version e we realize the observe-sequence@1.0.18 is broken on Internet Explorer 11

We believe is something related to the syntax, not supported, present here: https://github.com/meteor/blaze/blob/master/packages/observe-sequence/observe_sequence.js#L170

As a workaround, we are doing a downgrade to the v1.0.16: RocketChat/Rocket.Chat#22557
We hope you guys can have a fix for that soon, thanks!

[StorytellerCZ]

Confirmed, for-of loop is not compatible with IE at all. I'll get a fix out today.

[StorytellerCZ]

ping @antoinep92 who implemented this originally.

[antoinep92]

Sorry about that.
@StorytellerCZ you just downgraded or did you fix the implem (loop) ? If not, I can fix by tomorrow max.

[antoinep92]

Hum ok I saw your fix. Indeed it should work in IE, but breaks my code for non-array iterables.
e.g. toDebugStr(new Set([1,2,3]) returns "Set []".
I thought about using Array.from but that's not supported either.
Is there some kind of library you use that provides a polyfill or equivalent to Array.from, or should I implement it "by hand" (that would be a lot simpler than the proposed polyfill on MDN's page, because we only need to handle one special case) ? 🤔

[antoinep92]

After giving this some more thought: I can use Array.from safely, since it won't trigger a parse error in IE 11 (as for .. in did) and iterables aren't supported on IE either, so the branch with Array.from will be unreachable in IE. I'll submit a PR shortly.