Is there any other way to implement Singleton Pattern in javascript?

Question

Trying to implement singleton pattern in javascript following some tutorials. Just wondering if there is any other way to implement the same ?

var singleton = (function(){
              var getInstance; //private variable

              var createWidget = function(){
                         var todayDate = new Date(); //private
                         var addCSS = function(){
                            console.log('THis is my css function');
                         };
                         var getDropDownData = function(){
                            console.log('This is my getDropDownData function');
                         };
                         return {
                            getDropDownData : getDropDownData,
                            addCSS: addCSS 
                         };
              };

              return {
                    getInstance: function(){
                          if(!getInstance) {
                              getInstance = createWidget();
                          }
                          return getInstance;
                    }
              };
})();
var obj = singleton.getInstance();

Implementing it by running anonymous function at onLoad and assiging it to some variable. Can we implement it without running this function at onLoad ?

You can implement a singleton in many ways, if you want a more definitive answer then you would need to provide more details on exactly what it is you are trying to do. — James, Aug 16 '14 at 08:30
Nothing much, I just want single object for my class. We are dynamically creating widget with this function.I am looking for best and simple way for it. — Vivek Pratap Singh, Aug 16 '14 at 08:39
Is this possibly a duplicate to [this](http://stackoverflow.com/questions/1479319/simplest-cleanest-way-to-implement-singleton-in-javascript)? — masa, Aug 16 '14 at 08:44
What do you mean by "*can we implement it without running this function at onLoad*"? Well, yes, however, you need to elaborate what you mean. — James, Aug 16 '14 at 09:07
As new to design patterns, We follow philosphy like "Do it when need it". Write a function and call it. So looking around , which removes the onLoad call of this func. — Vivek Pratap Singh, Aug 16 '14 at 09:11

score 0 · Accepted Answer · answered Aug 16 '14 at 09:41

You could always write a function to abstract away the boilerplate for writing singletons. For example this is what I would do:

function singleton(prototype) {
    var instance = null;

    return {
        getInstance: function () {
            if (instance === null) {
                var Instance = prototype.init || function () {};
                Instance.prototype = prototype;
                instance = new Instance;
            } return instance;
        }
    };
}

Then you can use this function to create singletons as follows:

var Widget = singleton({
    init: function () {
        var todayDate = new Date; // private
    },
    addCSS: function () {
        console.log("This is my addCSS function.");
    },
    getDropDownData: function () {
        console.log("This is my getDropDownData function.");
    }
});

After that you use the singleton as you normally would:

var widget = Widget.getInstance();

Hope that helps.

Is there any other way to implement Singleton Pattern in javascript?

1 Answers1