sngleton-pattern

the Singleton Pattern ensures a class has only one instance, and provides a global access point to it.

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

    // Initialize your properties
    this.state = 'I am the only instance';
    
    // Lock the instance
    Singleton.instance = this;
  }

  getState() {
    return this.state;
  }

  setState(value) {
    this.state = value;
  }
}

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

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

✅ Best Practices Use closures or modules if you don't need a class. Avoid overusing it. Singleton = Global mutable state, which can be risky.

⚡ Module Pattern (Cleaner Singleton)

const Singleton = (function () {
  let instance;

  function createInstance() {
    return {
      state: 'I am the only instance',
    };
  }

  return {
    getInstance: function () {
      if (!instance) {
        instance = createInstance();
      }
      return instance;
    },
  };
})();

// Usage
const obj1 = Singleton.getInstance();
const obj2 = Singleton.getInstance();

console.log(obj1 === obj2); // true