Emulate Prototype Inheritance

emulate_inheritance.js

/* ===============
 * This snippet shows you how to inherit from one object into another,
 * without using the `new` keyword or using any functions.
 * ===============
 */

// create a class object which we will use to emulate inheritance
var Person = {
  firstname: 'John',
  lastname: 'Doe'
}

// explicitely provide a propertyname called `prototype` and make it an object
Person.prototype = {}

// add a method to the prototype
Person.prototype.sayname = function() {
  return `${this.firstname} ${this.lastname}`
}

// now, treat `Person` as a class, and let's make an instance of `Person`
//    but since, `Person` is actually an object, we cannot use the `new`
//    operator to make an instance of it. So ...

var p1 = {}     // create an empty object

// add some new values to the properties already provided
p1['firstname'] = 'Auto'
p1['lastname'] = 'Matic'

// we know that every object created with a `new` keyword 
//    has a `__proto__` property which pionts to the constructor's
//    prototype. So, let's emulate that here...

p1.__proto__ = Person.prototype                   // <--------------- INHERITANCE

console.log(p1.sayname())    // Auto Matic