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

Function Expressions and Static Behavior in JavaScript

When using the new keyword with a JavaScript function expression, some developers may mistakenly believe that the resulting object behaves statically. However, this assumption is not entirely accurate.

The new keyword creates a new instance of an object, and the function expression becomes the constructor for that instance. While the resulting object may exhibit some static-like behavior, such as being accessible without instantiation, it still has a constructor property that points to the anonymous function.

Consider the example provided:

var gameData = new function () {
  // ...
};

Even though the new keyword is used, it's still possible to instantiate additional objects using the gameData constructor:

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

This means that the gameData object is not truly static. Instead, the constructor property is being "leaked," allowing for multiple instances to be created. Additionally, a prototype object is created for gameData, which may introduce unnecessary complexity if private variables or inheritance is not intended.

To create a true singleton object in JavaScript, one should consider using a different pattern such as an object literal, revealing module pattern, or a dedicated constructor function that enforces a single instantiation.

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