BFE 1. Implement curry()

What is currying?

Currying is a functional programming technique that allows me to partcially apply a function by breaking down the parameters into a series of functions that each function takes some of the parameters.

Example

add(1, 2, 3) -> add(1)(2)(3)

add(1, 2, 3) -> add(1, 2)(3)

add(1, 2, 3) -> add(1)(2, 3)

Thoughts:

Need to return a function for chaining the calls until all the arguments are provided.

Tips:

Function.prototype.length:

get the number of parameters of a function.
Function.prototype.apply:

call a function with a given this value and arguments provided as an array.
Function.prototype.concat:

merge two or more arrays.

Code:

function curry(fn) {
  return function curried(...args) {
    if (args.length >= fn.length) {
      return fn.apply(this, args);
    } else {
      return function (...nextArgs) {
        return curried.apply(this, args.concat(nextArgs));
      };
    }
  };
}

Reference

Original link

Parameter vs Argument