JavaScript classes exist?

Question

I know classes do not exist in javascript.

But, Is there any indirect way to create a class in javascript?

what is the use of defining a class in javascript

Answer 1

JavaScript classes, introduced in ECMAScript 2015, are primarily syntactical sugar over JavaScript's existing prototype-based inheritance. The class syntax is not introducing a new object-oriented inheritance model to JavaScript. JavaScript classes provide a much simpler and clearer syntax to create objects and deal with inheritance.

Here are two examples using ES5 and ES6

'use strict';

/**
 * Shape class.
 * 
 * @constructor
 * @param {String} id - The id.
 * @param {Number} x  - The x coordinate.
 * @param {Number} y  - The y coordinate.
 */
function Shape(id, x, y) {
    this.id = id;
    this.setLocation(x, y);
}

/**
 * Set shape location.
 * 
 * @param {Number} - The x coordinate.
 * @param {Number} - The y coordinate.
 */
Shape.prototype.setLocation = function(x, y) {
    this.x = x;
    this.y = y;
};

/**
 * Get shape location.
 * 
 * @return {Object}
 */
Shape.prototype.getLocation = function() {
    return {
        x: this.x,
        y: this.y
    };
};

/**
 * Get shape description.
 * 
 * @return {String}
 */
Shape.prototype.toString = function() {
    return 'Shape("' + this.id + '")';
};

/**
 * Circle class.
 * 
 * @constructor
 * @param {String} id     - The id.
 * @param {Number} x      - The x coordinate.
 * @param {Number} y      - The y coordinate.
 * @param {Number} radius - The radius.
 */
function Circle(id, x, y, radius) {
    Shape.call(this, id, x, y);
    this.radius = radius;
}
Circle.prototype = Object.create(Shape.prototype);
Circle.prototype.constructor = Circle;

/**
 * Get circle description.
 * 
 * @return {String}
 */
Circle.prototype.toString = function() {
    return 'Circle > ' + Shape.prototype.toString.call(this);
};

// test the classes
var myCircle = new Circle('mycircleid', 100, 200, 50); // create new instance
console.log(myCircle.toString()); // Circle > Shape("mycircleid")
console.log(myCircle.getLocation()); // { x: 100, y: 200 }

'use strict';

/**
 * Shape class.
 * 
 * @constructor
 * @param {String} id - The id.
 * @param {Number} x  - The x coordinate.
 * @param {Number} y  - The y coordinate.
 */
class Shape(id, x, y) {
    constructor(id, x, y) { // constructor syntactic sugar
        this.id = id;
        this.setLocation(x, y);
    }
    
    /**
     * Set shape location.
     * 
     * @param {Number} - The x coordinate.
     * @param {Number} - The y coordinate.
     */
    setLocation(x, y) { // prototype function
        this.x = x;
        this.y = y;
    }
    
    /**
     * Get shape location.
     * 
     * @return {Object}
     */
    getLocation() {
        return {
            x: this.x,
            y: this.y
        };
    }
    
    /**
     * Get shape description.
     * 
     * @return {String}
     */
    toString() {
        return `Shape("${this.id}")`;
    }
}

/**
 * Circle class.
 * 
 * @constructor
 * @param {String} id     - The id.
 * @param {Number} x      - The x coordinate.
 * @param {Number} y      - The y coordinate.
 * @param {Number} radius - The radius.
 */
function Circle extends Shape {
    constructor(id, x, y, radius) {
        super(id, x, y); // call Shape's constructor via super
        this.radius = radius;
    }
    
    /**
     * Get circle description.
     * 
     * @return {String}
     */
    toString() { // override Shape's toString
        return `Circle > ${super.toString()}`; // call `super` instead of `this` to access parent
    }
}

// test the classes
var myCircle = new Circle('mycircleid', 100, 200, 50); // create new instance
console.log(myCircle.toString()); // Circle > Shape("mycircleid")
console.log(myCircle.getLocation()); // { x: 100, y: 200 }

More details here

Answer 2

Use this example.

    class Rectangle {
  constructor(height, width) {
    this.height = height;
    this.width = width;
  }

  get area() {
    return this.calcArea();
  }

  calcArea() {
    return this.height * this.width;
  }
}

const square = new Rectangle(10, 10);

console.log(square.area);

So basically, you can make classes, and they need to start with an "init" function which is usually the constructor function. You can add as many functions after that. NOTE: The code above was from: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes