🔬 Typescript cheatsheet

Typescript.ts

// Change last param of a function
type LastIndex<T extends readonly any[]> = ((...t: T) => void) extends (x: any, ...r: infer R) => void
    ? Exclude<keyof T, keyof R>
    : never;

type ReplaceLastParam<TParams extends readonly any[], TReplace> = {
    [K in keyof TParams]: K extends LastIndex<TParams> ? TReplace : TParams[K];
};

type ReplaceLast<F, TReplace> = F extends (...args: infer T) => infer R
    ? (...args: ReplaceLastParam<T, TReplace>) => R
    : never;

type ReplacedArg = { param: string };
type OriginFunc = typeof myFunction;

type NewFunc = ReplaceLast<OriginFunc, ReplacedArg>;
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