JavaScript prototyping

In JavaScript, every object has a prototype property. Prototype property is also an object. All JavaScript objects inherit there properties and methods from there prototypes.

Using prototypes makes object creation faster.

	function Person(name){
	this.name = name;
	}
	var person1 = {
	name : 'Person 1'
	};
	Person.prototype.getName = function(){
	return "Name of the person is " + this.name;
	};
	//Don't forget to put new keyword before Person
	var person2 = new Person('Person 2');
	console.log(person2.getName()); //Name of the person is Pook 2
	//This is not possible
	// Uncaught TypeError: Cannot set property 'getName' of undefined (anonymous function)
	/*
	person1.prototype.getName = function(){
	return "Name of the person is " + this.name;
	}
	*/

view raw js_prototype1.js hosted with ❤ by GitHub

When an inherited function is executed, the value of this points to the inheriting object, not to the prototype object where the function is an own property.

Object.create :  Create a new object with specified prototype object and properties

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Inheritance_and_the_prototype_chain

hasOwnProperty is an own property of Object.prototype. When we create an object, it inherits hasOwnProperty from Object.prototype.

Arrays inherits from Array.prototype (it has methods like forEach, call)

// f ---> Function.prototype ---> Object.prototype ---> null

The lookup time for properties that are high up on the prototype chain can have a negative impact on performance, and this may be significant in code where performance is critical. Additionally, trying to access nonexistent properties will always traverse the full prototype chain.

Also, when iterating over the properties of an object, every property that is on the prototype chain will be enumerated.

http://stackoverflow.com/questions/14034180/why-is-extending-native-objects-a-bad-practice

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create

http://stackoverflow.com/questions/572897/how-does-javascript-prototype-work