ES5 class extending

es5Extend.js

var assert = require('assert');

// Define parent "class"
var Parent = function Parent(name) {
  this.name = name;
  this.isYoung = false;
};

Parent.prototype.speak = function speak() {
  console.log('Hello, my name is ' + this.name);
  if (this.isYoung) {
    console.log('I am young!');
  } else {
    console.log('I am not young.');
  }
};

// Extend parent "class"
var Child = function Child(name) {
  Parent.apply(this, arguments);
  this.isYoung = true;
}

Child.prototype = Object.create(Parent.prototype);
Child.prototype.constructor = Child;

// Let's test it out
var lisa = new Parent('Lisa');
var abdul = new Child('Abdul');

lisa.speak();
abdul.speak();

// Assert type inherits
assert.equal(lisa instanceof Child, false);
assert.ok(lisa instanceof Parent);

assert.ok(abdul instanceof Child);
assert.ok(abdul instanceof Parent);