OOJS Revelations

arguments..js

function add() {
  var sum = 0;
  
  for (var i in arguments) {
    sum += arguments[i];
  }
  
  return sum;
}

add(2,4); // 6

closure.js

function add(a) {
  return function(b) {
    return a + b;
  }
} 

var sum = add(2);
sum(4); // 6

add(2)(4); // 6

hoisting.js

// The JavaScript engine hoists the function declaration to the top
fullName('Craig', 'Freeman'); // "Freeman, Craig"

function fullName(firstName, lastName) {
  return lastName + ', ' + firstName;
}

// The JavaScript engine only recognizes the function expression 
// as a variable
fullName('Craig', 'Freeman'); // Uncaught TypeError: undefined is not a function

var fullName = function(firstName, lastName) {
  return lastName + ', ' + firstName;
};

property_access.js

// Assuming there's an unknown amount of custom global Map objects
// window.Map1, window.Map3, window.Map5, etc.
var mapIds = [1, 3, 5, 7, 9],
  maps = [];

for (var i in mapIds) {
  maps[] = window.['Map' + i];
}