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Stop 1 of 5 · Library returns desk
Trick to keep in mind+3 XP
Generic = same type in, same type out, with a blank for TypeScript to fill
In firstOr<T>(items: T[], fallback: T): T, the T is a blank. TypeScript fills it in from the arguments you actually pass, and the return type uses the same filled-in value. That link between input and output is what a plain any cannot give you.
Read it once, then a question tests whether the trick stuck.