Immediate Instantiation of Anonymous Classes: A Cautionary Tale

In ES6, it's possible to define anonymous classes and instantiate them immediately. While this syntax may seem appealing at first, it's crucial to understand its pitfalls and why it should generally be avoided.

To instantiate an anonymous class directly, we use the following syntax:

var entity = new class {
    constructor(name) { this.name = name; }
    getName() { return this.name; }
}('Foo');

Behind the scenes, this results in the creation of a new constructor function and a prototype object for each instantiation. This means that multiple objects created using this method will not share any benefits from class inheritance or prototypal relationships.

Furthermore, this approach undermines attempts to create singleton objects using anonymous classes. The constructor function can still be accessed and utilized to create additional instances, negating the intended singleton behavior.

In light of these caveats, it's strongly recommended to avoid using immediately instantiated anonymous classes. Simpler object literals offer a more efficient and straightforward alternative:

var entity = {
    name: 'Foo',
    getName() { return this.name; }
};