Javascript new object (function ) vs inline invocation

Question

Is there any considerations to determine which is better practice for creating an object with private members?

var object = new function () { 
   var private = "private variable";
   return {
       method : function () { 
           ..dosomething with private;
       }
   }
}

VS

var object = function () {
 ...
}();

Basically what is the difference between using NEW here, and just invoking the function immediately after we define it?

Outguess

Never ever use new function(){…}! Admittedly, in this particular case where you return from the function it's not that bad. – Piwowar

Answer 1

The new operator causes the function to be invoked like a Constructor Function.

I've seen that pattern before, but I don't see any benefits of using it.

The purpose of the new operator is to create an object (the this value inside the constructor), setting the right [[Prototype]] internal property, to build the prototype chain and implement inheritance (you can see the details in the [[Construct]] operation).

I would recommend you to stay with the inline invocation pattern.

Maryellen

While I agree with CMS because you are using a revealing module pattern and relying on lexical scoping - I would clarify that new is appropriate when creating a class-like object built upon a prototype pattern - for example a BackboneJS Model or View. – Dayflower

Answer 2

If you're using functions as event handlers you can get memory leaks. Have a look at some of the articles

Guayule

Answer 3

This link provides statistics which also confirms that inline invocation pattern is better.

Please note that the measurement is in operations per second which the higher the better

Beeves