uncurry

Uncurries a function up to depth n.

• Return a variadic function.
• Use Array.prototype.reduce() on the provided arguments to call each subsequent curry level of the function.
• If the length of the provided arguments is less than n throw an error.
• Otherwise, call fn with the proper amount of arguments, using Array.prototype.slice(0, n).
• Omit the second argument, n, to uncurry up to depth 1.

const uncurry = (fn, n = 1) => (...args) => {
  const next = acc => args => args.reduce((x, y) => x(y), acc);
  if (n > args.length) throw new RangeError('Arguments too few!');
  return next(fn)(args.slice(0, n));
};

const add = x => y => z => x + y + z;
const uncurriedAdd = uncurry(add, 3);
uncurriedAdd(1, 2, 3); // 6