map() above, because in both cases we return a promise (or an array of promises) which we can await. TLDR: Only map(), reduce(), flatMap() and reduceRight() if used correctlyĪsync-await works naturally with for loops and while loops, because they are written in the original function body.īut when you call out to another function, it can only work with async-await if it returns a promise, and if that promise is handled (awaited or. You can decide on the trade-off between bundle size and developer convenience. for.of requires iterators, and some browsers require a polyfill for iterators, and that polyfill is quite large. However it is recommended by the Airbnb style guide because it can reduce the browser bundle size. This has pretty much the same behaviour as the for.of above, but is slightly harder to read. (We are using the accumulator a not as a total or a summary, but just as a way to pass the promise from the previous item's callback to the next item's callback, so that we can wait for the previous item to finish being processed.)

For each in typescript