§ What is a singleton and why we need it

Singleton pattern is a design pattern in which a class has only one instance and provides a global point of access to it. The idea is to create only one instance of a class and use that instance whenever required in the application.

In JavaScript, the Singleton pattern can be implemented by creating an object and returning its reference. Here's an example:

let instance = null;

class Singleton {
  constructor() {
    if (!instance) {
      instance = this;
    }
    return instance;
  }
}

const a = new Singleton();
const b = new Singleton();

console.log(a === b); // true