singleton.js

/**
 * Singleton Pattern
 */
function Singleton(options) {

    if (!(this instanceof Singleton) && Singleton.getInstance === undefined) {
        Singleton.getInstance = new Singleton();
        return Singleton.getInstance;
    }

    if (Singleton.getInstance !== undefined) {
        return Singleton.getInstance;
    }

    this.init();
}

Singleton.prototype.init = function () {
    // Some code!

    return this;
}