Singleton Design Pattern - Javascript

Singleton Design Pattern - Javascript

Singleton Design Pattern

What is Singleton Design Pattern?

  • Singleton design pattern is one of the creational design patterns.
  • Singleton design pattern describes how the object should be created.
  • It ensures that the class has only one instance and provides a global access point to that instance.
  • Singleton design pattern is discovered because of bugs due to multiple instances where only one instance should be present.

When to use Singleton Design Pattern

  • We need to ensure only one instance of the class is present.
  • We need to provide a global access point to a class instance.

Code example

  • A logger is one of the real-world use cases in which we want to have a single instance globally.
let instance = null;

class Logger {
    constructor(logger_name) {
        if (!instance) {
   = logger_name;
            instance = this;
        } else {
            return instance;

const logger_1 = new Logger('Logger1');
const logger_2 = new Logger('Logger2');

console.log(logger_1); // Logger {name: 'Logger1'}
console.log(logger_2); // Logger {name: 'Logger1'}
  • In this example, you can see that even if we try to create 2 different instances of the Logger class there will be only one instance of the Logger class.
  • You can find the code in the GitHub repository.
  • This is how we can use singleton in javascript.

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