currify.js

function currify(f) {
  return function _currify(flen, _f) {
    return (...args) => {
      var remaining = flen - args.length;
      return remaining <= 0 ?
        _f(...args) :
        _currify(remaining, (...args2) => _f(...args, ...args2));
    };
  }(f.length, f);
}


function add(a, b, c) { return a + b + c; }
var _add = currify(add);

console.log(_add(1)(2)(3));
console.log(_add(1, 2)(3));
console.log(_add(1)(2, 3));
console.log(_add(1, 2, 3));