Currying

curry-3.js

function realSum(a, b) {
  return a + b;
};

console.log(realSum(5, 3)); // 8

var sum5 = curryIt(realSum, 5);
console.log(sum5(4)); // 9

var sum3 = curryIt(realSum, 3);
console.log(sum3(4)); // 7

currying-1.js

function realSum(a, b) {
  return a + b;
};

function sum(a, b) {

  return b ?
    realSum(a, b) :
    function(b) {
      // This anonymous function has access to variable `a` via closure
      return realSum(a, b);
    }
}

console.log(sum(5, 3)); // 8

var sum5 = sum(5);
console.log(sum5(4)); // 9

var sum3 = sum(3);
console.log(sum3(4)); // 7

curryIt.js

var curryIt = function(fn) {
  var fnArgsWhileBeingCurried = Array.prototype.slice.call(arguments, 1);
  return function() {
  	var fnArgsAfterBeingCurried = Array.prototype.slice.call(arguments, 0); 
  	return fn.apply(this, fnArgsWhileBeingCurried.concat(fnArgsAfterBeingCurried));
  };
};