Intro to JavaScript Classes Static Methods

Learning objective: By the end of this lesson, students will understand the role of static methods in JavaScript classes.

Static methods

Static methods are typically used to implement behavior that does not pertain to a particular instance. These are callable on the class itself - not on its instances. For example, we could design the Car class so that it tracks every car it creates. We could then write static methods that return how many cars have been created, search for them by their make, and more.

Here’s how to define a basic static method:

class Car {
  // the constructor will always be called
  constructor(make, model, color) {
    this.make = make;
    this.model = model;
    this.color = color;
    this.isRunning = false;
  }
  start() {
    this.isRunning = true;
    console.log('Running!');
  }
  static about() {
    console.log('I\'m the Car class!');
  }
};

đŸ’¡ Notice the use of the static keyword that prefaces the method’s name.

Next, let’s call upon the static about method:

Car.about(); // I'm the Car class!

If we attempt to call about on the mySubaru instance, we should get an error:

mySubaru.about(); // Uncaught TypeError: mySubaru.about is not a function