Javascript - Abstract Class Design Pattern

js-abstract-class.js

var testChildClass = new ChildClass(5, "A child class property!");

console.log(testChildClass.basePropertyThree); // '5'

console.log(testChildClass.anotherProperty); // 'A child class property!'

console.log(testChildClass.baseFunction()); // '7'

testChildClass.childFunction('Hello world!'); // 'Hello world!'

js-base-class.js

function BaseClass(param1) {
  
  if (this.constructor === BaseClass) {
    throw new Error("Can't instantiate abstract class!");
  }

  this.basePropertyOne = "Property1";
  this.basePropertyTwo = 2;
  this.basePropertyThree = param1;

}

BaseClass.prototype.baseFunction = function() {
  return this.basePropertyTwo + this.basePropertyThree;
}

js-child-class.js

function ChildClass(parameterToBase, normalParameter) {
  
  // We want to use 'apply', and not 'call' for this.
  // See: http://stackoverflow.com/a/1986909/4768230 for why.
  BaseClass.apply(this, arguments);
  
  // 'parameterToBase' will be sent down to the 'base' class.
  this.anotherProperty = normalParameter;
  
}

ChildClass.prototype = Object.create(BaseClass.prototype);
ChildClass.prototype.constructor = ChildClass;

ChildClass.prototype.childFunction = function(string) {
  console.log(string);
}