JavaScript class declaration

Definition and usage

A class is a function, but it is initialized not with the keyword function, but with the keyword class, and attributes are assigned in the constructor() method.

The constructor() method is called each time a class object is initialized.

Note:Unlike functions and other JavaScript declarations, class declarations are not hoisted (you must declare a class first before you can use it).

Note:The syntax in the class must be written in "strict mode".

For more information about classes, please read our JavaScript classes tutorial.

Instance

Create a Car class and then create an object named "mycar" based on the Car class:

class Car {  // Create class
  constructor(brand) {  // Constructor
    this.carname = brand;  // Class body
  }
}
mycar = new Car("Ford");  // Create an object of Car class

Try it yourself

Syntax

class className {
  // Class body
}

Technical details

JavaScript version: ECMAScript 2015 (ES6)

Browser support

The following table defines the first browser versions that fully support JavaScript classes:

Keywords Chrome IE Firefox Safari Opera
class 49.0 12.0 45.0 9.0 36.0

Related pages

JavaScript Tutorial:JavaScript Class

JavaScript Tutorial:JavaScript ES6 (EcmaScript 2015)

JavaScript Tutorial:JavaScript this

JavaScript Tutorial:JavaScript Strict Mode