Explain the concept of the Singleton pattern

The Singleton pattern ensures that a class has only one instance and provides a global point of access to that instance. This is useful when exactly one object is needed to coordinate actions across the system. In JavaScript, this can be implemented using closures or ES6 classes.

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

const instance1 = new Singleton();
const instance2 = new Singleton();

console.log(instance1 === instance2); // true