How do I create an abstract base class in JavaScript?

Question

Is it possible to simulate abstract base class in JavaScript? What is the most elegant way to do it?

Say, I want to do something like: -

var cat = ne         


        

Answer 1

We can use Factory design pattern in this case. Javascript use prototype to inherit the parent's members.

Define the parent class constructor.

var Animal = function() {
  this.type = 'animal';
  return this;
}
Animal.prototype.tired = function() {
  console.log('sleeping: zzzZZZ ~');
}

And then create children class.

// These are the child classes
Animal.cat = function() {
  this.type = 'cat';
  this.says = function() {
    console.log('says: meow');
  }
}

Then define the children class constructor.

// Define the child class constructor -- Factory Design Pattern.
Animal.born = function(type) {
  // Inherit all members and methods from parent class,
  // and also keep its own members.
  Animal[type].prototype = new Animal();
  // Square bracket notation can deal with variable object.
  creature = new Animal[type]();
  return creature;
}

Test it.

var timmy = Animal.born('cat');
console.log(timmy.type) // cat
timmy.says(); // meow
timmy.tired(); // zzzZZZ~

Here's the Codepen link for the full example coding.