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Abstract Class

An abstract class, sometimes also called a template, is a class from which an object cannot be instantiated directly.

As of July 2017, there is no native support for abstract classes and interfaces. However, you can do the following:


class Food {
  constructor(b) {
    if (new.target === Food) // or: this.contructor === Food
      throw new TypeError("Cannot instantiate from an Abstract Class directly! Food");
    if (this.brand === undefined)
      throw new TypeError("brand() must be defined -- Food");
  }
}

class DogFood extends Food {}

// var h = new Food;
var o = new DogFood;

Uncaught TypeError: brand() must be defined -- Food (if "var h = new Food;" above were uncommented, it would throw first: Uncaught TypeError: Cannot instantiate from an Abstract Class directly! Food)

Every time a 'new' keyword is used to instantiate an object (eg. new Food), the class (ie. Food)is assigned to a meta property, new.target, which can be accessed within the constructor.