It helps avoiding number of arguments problems, though. Of course it doesn't change the core semantics of JS.
This issue is all about the number of arguments problem, and TypeScript (in cases like this) won't flag that problem. Which is something I think it should.
If you manually unroll the "map" and call parseInt() explicitly with the same arguments that map() calls parseInt() with, TypeScript will flag that. But not when map() is in the picture.
I understand why they chose to do that, but I still disagree with it.
error TS2345: Argument of type '(string: string, radix?: number) => number' is not assignable to parameter of type '(value: string, index: number, array: string[]) => number'. Target signature provides too few arguments. Expected 3 , but got 2.
console.log(["1","2","3"].map(parseInt));
I'm curious - have you been using this for long? Have you noticed any code which this flagged and which you thought it was being too strict? I feel like I would want this flag on all of the time, but I'm curious if there are edge cases that I have not considered but maybe you have experienced.
If I do not want to change existing code to add parameters for each callback I use trick bellow : type JavaScriptCallback< T extends (...args: any) => any, P = Parameters<T> > = P extends [...infer Rest, infer _Last] ? ((...args: Rest) => ReturnType<T>) | JavaScriptCallback<T, Rest> : T;
interface Array<T> { forEach( callbackfn: JavaScriptCallback<(value: T, index: number, array: T[]) => void>, thisArg?: any ): void;
map<U>(
callbackfn: JavaScriptCallback<(value: T, index: number, array: T[]) => U>,
thisArg?: any
): U[];