Creating objects in JavaScript

I've been messing around with JavaScript for years now, but have been more of a JQuery hacker. I thought it was time to learn the language properly as its becoming increasingly common in web applications these days. This is a bit of a dummies guide, but I guess you need to start somewhere... JavaScript is a dynamically typed language where objects can be throught of as groups of properties. A property can one of six basic types: numbers, strings, Booleans, objects, functions, and undefined values.

'use strict'

// An empty JavaScript object
var myEmpty = {};

// Create an object using object literals
var monkey = { name: "John", age: 23, color: "blue" };

console.log(monkey.name)        // John

// You don't actually need to declare a property for it to be there:
monkey.height = 200;

console.log(monkey.height)      // 200

// A property can also be a function
var gorilla   = { name: "ted", age: 42, color:function() { return "orange" } };

console.log(gorilla.color())    // orange

// we can create new objects using a constructor function
function Monkey(name, color) {
    this.name = name;
    this.color = color
}
var bill = new Monkey("bill", "pink");

// bill is a new object
console.log(bill.color); // pink

When we create an object using a constructor function in JavaScript the new keyword is syntactic sugar for Object.create. The function Monkey is just a normal function. If we don't use the keyword new, then this refers to the current global context which, for a webpage, would be the window object. When we do use new a new object is created and the context of this is set to the new object. The capital letter of the Monkey function is of course just a style preference. Here is the same example, but using the Object.create method. notice that we have to set alot of meta data about each of the properties.

'use strict'

var monkey = Object.create(Object.prototype,
                {
                    name: {
                        value: "Hansel",
                        writable: true,
                        enumerable: true,
                        configurable: true
                    },
                    color: {
                        value: "Brown",
                        writable: true,
                        enumerable: true,
                        configurable: true
                    }
                });

console.log(monkey.name); // Hansel

In ECMA 6 there is a new class keyword for creating objects. Its actually just syntatic sugar for creating exactly the same as above:

'use strict'

  class Monkey {
      constructor(name, color) {
          this.color = color;
          this.name = name;
      }
  }

  var bert = new Monkey("albert", "red");
  
  console.log(bert.name)      // albert