IDK, in JS I love reduce and think it is invaluable. If you don't care about closures, never used underscore/lodash, and have not written several hundred var self = this; then you don't share my pain. IMO fat arrow const/let kids don't know about walking uphill to school both ways. Also I agree with commenters who use prev instead of acc, it is much easier on my brain to use prev.

TypeScript basically ruined reduce for me though, so there is that.