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JavaScript Classes | Fundamentals

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JavaScript Classes are a template for creating objects. A class encapsulates data and functions (methods) that manipulate data. Use the keyword class to create a class.

class ClassName {
  constructor() { ... }
}

The constructor method is a special method for creating and initializing an object created with a class. There can only be one special method with the name “constructor” in a class.

Use the super keyword to call the constructor of the superclass.

JavaScript Classes

A simple example creates a class named “Car” with two initial properties: “name” and “year”. Use the class by creating objects:

<!DOCTYPE html>
<html>
<body>
  <script>

    class Car {
      constructor(name, year) {
        this.name = name;
        this.year = year;
      }
    }
    let myCar1 = new Car("Tesla", 2008);
    let myCar2 = new Car("BMW", 1916);

    console.log(myCar1)
    console.log(myCar2)
  </script>
</body>
</html> 

Output:

JavaScript Classes

You can add any number of methods in the class.

class ClassName {
  constructor() { ... }
  method_1() { ... }
  method_2() { ... }
  method_3() { ... }
}

Example

class Car {
      constructor(name, year) {
        this.name = name;
        this.year = year;
      }
      age() {
        let date = new Date();
        return date.getFullYear() - this.year;
      }
    }
    let myCar1 = new Car("Tesla", 2008);
    let myCar2 = new Car("BMW", 1916);


    console.log(myCar1.age())
    console.log(myCar2.age())

Output: 14

106

It is easy to define methods in the JavaScript class. You simply give the name of the method followed by (). For example,

class Person {
    constructor(name) {
    this.name = name;
  }

    // defining method
    greet() {
        console.log(`Hello ${this.name}`);
    }
}

let person1 = new Person('John');

// accessing property
console.log(person1.name); // John

// accessing method
person1.greet(); // Hello John

Do comment if you have any doubts or suggestions on this JS basics topic.

Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.

OS: Windows 10

Code: HTML 5 Version

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