closureFactory.js

function createEngineFactory(radiusDefault) {
    /*
      Class methods.
     */
    function turnOn(self) {
        self.running = true;
    }

    function turnOff(self) {
        self.running = false;
    }

    function setRadius(self, radius) {
        self.radius = parseInt(radius, 10);
    }
    function printStatus(self) {
        console.log(`STATUS: Engine is ${self.running ? 'on' : 'off'} and radius is ${self.radius}`);
    }

    return function () {
        // Define data.
        let self = {
            running: false,
            radius: radiusDefault,
        };
        // Bind methods as partials of classmethods with self as the first argument.
        // Just ignoring `this` completely right now.
        self.turnOn = function () { turnOn.call(null, self) };
        self.turnOff = function () { turnOff.call(null, self) };
        self.setRadius = function (radius) { setRadius.call(null, self, radius) };
        self.printStatus = function () { printStatus.call(null, self) };
        return function (msg) {
            if (msg === 'turnOn') {
                self.turnOn();
            } else if (msg === 'turnOff') {
                self.turnOff();
            } else if (msg === 'setRadius') {
                self.setRadius(arguments[1]);
            } else if (msg === 'printStatus') {
                self.printStatus();
            } else {
                throw `Invalid method ${msg}`
            }
        }
    }
}

let Engine = createEngineFactory(15);

let engine1 = Engine()
engine1('printStatus')
engine1('turnOn')
engine1('printStatus')
engine1('turnOff')
engine1('printStatus')
engine1('setRadius', 100)
engine1('printStatus')

let engine2 = Engine()
engine1('turnOn')
engine2('turnOff')
engine1('printStatus');
engine2('printStatus');