Prototype inheritance in Javascript

prototype_inheritance.js

// Snippet showing inheritance through prototypes

var Animal = function(type){
    this.type = type;
};
Animal.prototype.eat = function(){
	console.log("They eat food to survive.");
};

var Mammal = function(){};

// Mammal inherits from Animals
Mammal.prototype = new Animal();        

Mammal.prototype.giveBirth = function(){
	console.log("They give birth to young ones.");  
};

var elephant = new Mammal(); //Creating instance of type Mammal
elephant.eat();              //elephant can use the inherited method from Animal.
elephant.giveBirth();

console.log(elephant instanceof Mammal);    // true
console.log(elephant instanceof Animal);    // true