[thomasrognon]

TypeScript is following JavaScript, not the other way around. Generally, ECMAScript proposals get added to TypeScript when they hit stage 3. Optional chaining and nullish coalescing were added to V8/Chrome and TypeScript around the same time.

[brlewis]

Yes, TypeScript adds features from the ECMAScript standard. Sometimes JS implementations add them around the same time TypeScript adds them. But sometimes TS adds them much earlier. Having been using TS, it surprised me in this article that nodejs didn't add numeric separators until recently. I had to check MDN to make sure it was right. TS, with or without Babel, keeps me from having to know what features are supported where. I used to frequently check MDN and caniuse.com out of necessity. Now I check infrequently out of curiosity.