JavaScript Classes

DeclarationAnonymous ClassExpression

class Rectangle {
    constructor(height, width) {
        this.height = height;
        this.width = width;
        this.area = this.calcArea();
    }
    get area() {
        return this.calcArea();
    }
    calcArea() {
        return this.height * this.width;
    }
}

const Rectangle = class {
    constructor(height, width) {
        this.height = height;
        this.width = width;
        this.area = this.calcArea();
    }
    get area() {
        return this.calcArea();
    }
    calcArea() {
        return this.height * this.width;
    }
};

const Rectangle = class Rectangle {
    constructor(height, width) {
        this.height = height;
        this.width = width;
        this.area = this.calcArea();
    }
    get area() {
        return this.calcArea();
    }
    calcArea() {
        return this.height * this.width;
    }
};

Instance

const rect = new Rectangle(10, 20);
console.log(rect.area); // 200

General Class Structure

class ClassName {
    instanceField;
    static staticField;
    #privateField;
    static #privateStaticField;

    constructor(value) {
        this.property = value;
        this.#privateProperty = value;
    }
    get property() {
        return this.property;
    }
    set property(value) {
        this.property = value;
    }
    method(parameter) {
        // code with this.* and parameter
    }
    static method(parameter) {
        // code withouth this.*
    }
    #privateMethod() {
        // code with this.* and parameter
    }
}

• instanceField is a field accessible from all instances of the class
• constructor() method which builds the class instance
• get and set methods for properties (accessors)
• static methods and fields are only accessible from the class itself ClassName.method()

Class Inheritance

class A {
    constructor(value) {
        this.a = value;
    }
    methodA() {
        console.log("A");
    }
}

class B extends A {
    constructor(value1, value2) {
        super(value1);
        this.b = value2;
    }
    methodB() {
        console.log("B");
    }
}

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