what is the use of javascript static methods on classes

1// Classes : static methods in javascript classes 
2
3class Square {
4    constructor(width){
5        this.width = width ;
6        this.height = width ;
7    }
8
9    static equals(a , b){
10        return a.width * a.height === b.width * b.height ;
11    }
12
13    static validDimensions(width , height ){
14        return width === height ;
15    }
16}
17
18console.log(Square.validDimensions(8 , 8));
19console.log(Square.validDimensions(10 , 12));
20console.log(Square.validDimensions(0 ,0 ));
21console.log(Square.validDimensions(2 , 3));
22console.log(Square.validDimensions(-3 , -3));

1class Hi {
2	constructor() {
3      console.log("hi");
4    }
5   	my_method(){}
6  	static my_static_method() {}
7}
8
9function getStaticMethods(cl) {
10  return Object.getOwnPropertyNames(cl)
11}
12
13console.log(getStaticMethods(Hi))
14// => [ 'length', 'prototype', 'my_static_method', 'name' ]
15

1// *** JS Class STATIC method ***   
2
3class Animal {
4        sayHello() {
5            return `${this.constructor.greeting}! I'm ${this.name}!`;
6        }
7    }
8
9    class Cat extends Animal {
10        constructor(name) {
11            super(); // connects parent to child/constructor
12            this.name = name; //=> need this line otherwise name undefined
13        }
14        static greeting = 'Feed me';
15    }
16
17    class Dog extends Animal {
18        constructor(name) {
19            super();
20            this.name = name; // same output type as above
21        }
22        static greeting = 'Sigh';
23    }
24
25    const run = document.getElementById("run");
26    run.addEventListener('click', () => {
27        let Garfield = new Cat('Garfield');
28        let Snoopy = new Dog('Snoopy');
29        console.log(Garfield.sayHello());
30        console.log(Snoopy.sayHello());
31    })
32// output = Feed me! I'm Garfield! Sigh! I'm Snoopy!

1// javascript static methods on Classes are called via the Class Name not  via the class Instances
2class Square {
3    constructor(width){
4        this.width = width ;
5        this.height = width ;
6    }
7
8    static equals(a , b){
9        return a.width * a.height === b.width * b.height ;
10    }
11}
12
13
14const newSquare1 = new Square(10);
15const newSquare2 = new Square(9);
16const newSquare3 = new Square(5);
17const newSquare4 = new Square(5);
18console.log(Square.equals(newSquare1 , newSquare2));
19console.log(Square.equals(newSquare3 , newSquare4));