There are scenarios in which only one instance of the specific class should ever exist, and that leads to Singleton Pattern.
The simplest singleton in JavaScript is an object literal; it provides a quick and cheap way to create a unique object:
const singleton = {
foo(): void {
console.log('bar');
}
};
But sometimes we might want private variables:
const singleton = (() => {
let bar = 'bar';
return {
foo(): void {
console.log(bar);
}
};
})();
Or we want to take the advantage of an anonymous constructor function or class expression in ES6:
const singleton = new class {
private _bar = 'bar';
foo(): void {
console.log(this._bar);
}
} ();