jsschools

class

Declares a class with a constructor, methods, and optional inheritance.

Since ES2015 (ES6) Spec ↗

Syntax

class Name extends Parent {
  constructor(...) { ... }
  method() { ... }
}

Returns

undefined — A class declaration is a statement and does not produce a value.

Examples

class Point {
  constructor(x, y) {
    this.x = x;
    this.y = y;
  }
  toString() {
    return `(${this.x}, ${this.y})`;
  }
}
console.log(new Point(1, 2).toString());
Output 
(1, 2)

class Animal {
  speak() { return "..."; }
}
class Dog extends Animal {
  speak() { return "Woof"; }
}
console.log(new Dog().speak());
Output 
Woof

class Counter {
  #count = 0;
  increment() { return ++this.#count; }
}
const c = new Counter();
console.log(c.increment());
Output 
1

Notes

- Class declarations are not hoisted in a usable way; they are in the temporal dead zone until evaluated. - Class bodies always run in strict mode. - Private fields use a `#` prefix and are only accessible inside the class body.

Browser & runtime support

EnvironmentSince version
chrome 49
firefox 45
safari 9
edge 13
node 6.0

See also