How Can I Properly Implement a Static Class or Singleton Pattern in JavaScript?

Understanding Javascript Static Function Expressions: The GameData Case

In Javascript, function expressions that utilize the new keyword are not static in the same sense as their C# counterparts. Rather than creating a genuinely static class, this approach leaks the constructor property and generates a prototype object that is likely not intended.

A Deeper Dive into the GameData Example

The provided example, gameData, demonstrates the creation of a single instance of a "class" using a function expression with the new keyword. However, the inclusion of the constructor property allows for the instantiation of additional objects, making the "class" non-static.

Alternative Singleton Approaches

To achieve a true singleton pattern in Javascript, consider the following methods:

• Object Literal: Create a simple object literal that lacks a constructor and prototype.
• Revealing Module Pattern: Employ an Immediately Invoked Function Expression (IIFE) to establish closure-scoped variables and return the desired object.
• Constructor ("Class"): Define a constructor function that, when called, always returns the same singleton object.

Singleton Pattern Implementation

The below code illustrates the Singleton Pattern using a constructor function:

function GameData() {
    if (this.constructor.singleton)
        return this.constructor.singleton;
    else
        this.constructor.singleton = this;

    // Private and public members initialization
}
GameData.prototype.storageAvailable = function () {
    // Availability check logic
};

var gameData = new GameData();
var gameData2 = new GameData();
console.log(gameData === gameData2 === GameData.singleton); // Outputs true

This approach ensures that subsequent instantiation attempts always return the same GameData instance, establishing a true singleton behavior.

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