curry.js

// bad 
function Curry(fn) {
  var args = Array.prototype.slice.call(arguments, 1);
  var len = fn.length - args.length;

  var partial = function () {
    var partialArg = Array.prototype.slice.call(arguments);
    args = args.concat(partialArg);
    if (args.length > len) {
      throw new Error('wrong argument lenth: Expected ' + len + '; Receive ' + args.length);
    }
    if (args.length === len) {
      return fn.apply(this, args);
    }
    return partial;
  }

  return partial();
}

// good
function Curry(fn) {
  var args = Array.prototype.slice.call(arguments, 1);
  var len = fn.length;

  function _curry(len, args, fn) {

    if (len < args.length)
      throw new Error('wrong argument lenth: Expected ' + len + '; Receive ' + args.length);

    if (len === args.length)
      return fn.apply(this, args);

    return function() {
      return _curry(len,
        args.concat(Array.prototype.slice.call(arguments)),
        fn);
    };
  }

  return _curry(len, args, fn);
}

// pointless^H^H^H^Hfree
function Curry(fn) {

  function curried(args) {

    if (fn.length <= args.length)
      return fn.apply(this, args);

    return function() {
      return curried(
        args.concat(Array.prototype.slice.call(arguments))
        );
    };
  }

  return curried(Array.prototype.slice.call(arguments, 1));
}


// true pointless
function Curry(fn, ...args) {

  return (function curried(args) {

    if (fn.length <= args.length) {
      return fn.apply(this, args);
    }
    return (...newArg) => curried(args.contact(newArg))
  })(args)

}

Failed because side effect in args