#449 Curry

easy
javascript

Currying is a functional-programming technique that transforms a function with N parameters into a series of functions that each take one or more of those parameters.
In everyday JavaScript development, currying enables elegant composition patterns and partial application.

Your task is to write a generic curry helper.

Function signature

function curry<F extends (...args: any[]) => any>(fn: F): Curried<F>;

Curried<F> must satisfy these rules at runtime:

  1. The returned function keeps accepting arguments until it has received all parameters required by the original fn.
  2. Each call may supply one or more arguments.
  3. Once the total argument count is met, invoke fn and return its result.
  4. Additional calls after completion are out of scope and may be ignored.

Examples

const join = (a: string | number, b: string | number, c: string | number) => `${a}_${b}_${c}`;
const curriedJoin = curry(join);

curriedJoin(1, 2, 3);     // '1_2_3'
curriedJoin(1)(2, 3);      // '1_2_3'
curriedJoin(1, 2)(3);      // '1_2_3'

Further reading: