Is a JavaScript Function Expression with `new` Truly Static?

Is a Javascript Function Expression Using 'new' Keyword Truly Static?

In an attempt to create a static-like class in Javascript without using a constructor or instantiation, code was written as such:

var gameData = new function () {
    //May need this later 
    this.init = function () { };

    this.storageAvailable = function () {
        if (typeof (Storage) !== "undefined") {
            return true;
        }
        else {
            return false;
        }
    };
}

The assumption is that the 'new' keyword prevents instantiation and makes the function expression behave like a static class. However, this is not entirely accurate.

Understanding the 'Static' Concept in Javascript

In Javascript, a static property or method is not bound to an instance of a class. It belongs to the class itself, regardless of whether any instance exists. Static members are typically shared by all instances of a class.

Limitations of the Function Expression Approach

Despite the 'new' keyword, the function expression still has a constructor property. This means it can be reinstated using the following code:

var gameData2 = new (gameData.constructor)();

This creates a separate instance of the function expression, negating the intended static behavior. Additionally, the prototype chain contains a useless prototype object for the function expression.

Alternatives to 'Static' Implementation in Javascript

To achieve true static behavior, consider these alternatives:

• Object Literal: Use a simple object literal to define properties and methods without a constructor.
• Revealing Module Pattern: Enclose the object literal in an IIFE (Immediately Invoked Function Expression) to create closure-scoped variables.
• Constructor 'Class': Define a constructor function that returns the same singleton object upon instantiation.

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