What is Singleton Pattern?

The singleton pattern is a design pattern that restricts the instantiation of a class to one object, much inspired from singleton set {0}.

Where is it useful?

• Controlling concurrent access to a shared resource.

• Abstract Factory implementation.

• One time read variables. etc

What is the use of it?

Well despite the arguments and down votes for Singleton Pattern, it's still surviving! And in JS it's useful for :

• Encapsulation of members & functions.

• Creating Namespace.

• Encourages code reuse.

• Logically organisation of code gets easier.

Singleton implementation with JavaScript :

function SalarySingleton() {
 
  if (typeof Singleton.salary === 'object') {
 
    return Singleton.salary;
 
  }
 
  this.setSalary = function(amt) {
    this.amt = amt;
  }
  this.getSalary = function() {
    return this.amt;
  }
 
  Singleton.salary = this;
 
}
 
var emp1 = new SalarySingleton();
emp1.setSalary(60000);

Do express your <3 towards singleton pattern!

EDIT 0 : iife to avoid new.

var singleton = (function () { 
    var amt; 
    return { 
        getSalary: function () { return amt; }, 
        setSalary: function (amount) { amt = amount; }}; 
    }
());