curry.js

curry.js

function curry( fn, arity ) {
  //var arity = fn.length;

  return (function resolver() {
    let mem = Array.prototype.slice.call( arguments );
    return function() {
      let args = mem.slice();
      Array.prototype.push.apply( args, arguments );
      return ( args.length >= arity ? fn : resolver ).apply( null, args );
    };
  }());
}

example.js

let multN = function(...args) {
  return args.reduce( (acc, cur) => acc * cur, 1 )
}

let mult3 = curry(multN, 3)  // specify arity as 2nd argument
let mult4 = curry(multN, 4) // specify arity as 2nd argument

console.log( mult3(1,2,3) ) // 6
console.log( mult3(1,2)(3) ) // 6
console.log( mult3(1)(2)(3) ) // 6

console.log( mult4(1)(2)(3)(4) ) // 24
console.log( mult4(1,2)(3)(4) ) // 24
console.log( mult4(1,2,3,4) ) // 24