[RhythmFox]

He also points out a pointless type check in a type checked language...

Your name is very accurate I must say.

[jazzypants]

That type check is honestly not pointless at all. You can never be certain of your inputs in a web app. The likelihood of that parameter being something other than an arraybuffer is non-zero, and you generally want to have code coverage for that kind of undefined behavior. TypeScript doesn't complain without a reason.