JavaScript reference

class

Declares a class — a template for objects with shared methods.

Available since: ES2015

Syntax

class Name { constructor() { … } method() { … } }

Examples

A class with a constructor and a method:

class User {
  constructor(name) {
    this.name = name;
  }
 
  greet() {
    return `Hi, I am ${this.name}`;
  }
}
 
const anna = new User('Anna');
 
console.log(anna.greet());

Output:

Hi, I am Anna

Class fields with default values:

class Counter {
  count = 0;
 
  increment() {
    this.count++;
    return this;
  }
}
 
const counter = new Counter();
counter.increment().increment();
 
console.log(counter.count);

Output:

Notes

The constructor runs automatically on new and fills in the object's properties. Class methods are shared by all its objects and are not copied into each one.

Code inside a class always runs in strict mode. A class cannot be called without new.

In the tutorial

Classes and objects — Classes in JavaScript: declaring a class, the constructor, fields, methods, this and creating objects with new.

Thanks for reading!