Web Developer Reference

Singleton pattern is when an object can be instantiated only once

  • useful for coordinating system wide state and actions
  • Reduces name collisions and need for too many global variables
  • Usually implemented as an IIFE
  • Examples include:
    • Redux store
    • database connection pool
    • JQuery module pattern
var Singleton = (function() {
    var instance;

    function createInstance() {
        var object = new Object('I am the instance');
        return object;
    }

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

            return instance;
        }
    }
})();

function run() {
    var instance1 = Singleton.getInstance();
    var instance2 = Singleton.getInstance();

    alert(`Same instance? + ${instance1 === instance2}`)
}

run();

References

https://www.dofactory.com/javascript/singleton-design-pattern https://learn.jquery.com/code-organization/concepts/