In what situation do we need to implement singleton class in javsacript

Question

In what scenario do we need to implement Singleton Class in javascript as below

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));  
}

Controlling any ressource that needs or should be unique in its environment. Eg. libraries, an overlaid drawing canvas, a specific parser ... — collapsar, Mar 12 '15 at 13:12

score 0 · Answer 1 · answered Mar 12 '15 at 13:18

The singleton pattern is a design pattern that restricts the instantiation of a class to one object. This is useful when exactly one object is needed to coordinate actions across the system. The concept is sometimes generalized to systems that operate more efficiently when only one object exists, or that restrict the instantiation to a certain number of objects. The term comes from the mathematical concept of a singleton.

The simplest singleton implementation in JavaScript is:

var Singleton = {};

What are the benefits we get from this implementation:

It instantiates only a single object
It is safe – it keeps the reference to the singleton inside a variable, which lives inside a lexical closure and is not accessible by the outside world
It allows you to initialize the singleton with some arguments. The module pattern, which wraps the singleton is not aware of the initialization arguments – it simply forwards the call with apply
You can use the instanceof operator

"*It allows you to initialize the singleton with some arguments.*" doesn't really make sense. If it's a singleton, there is only one valid way to initialise it, so you would just hardcode that. — Bergi, Feb 08 '18 at 05:17

In what situation do we need to implement singleton class in javsacript

1 Answers1