Singleton Pattern Example Printer

printer.js

var printer = (function () {

    var printerInstance;

    function create() {
        var turnedOn = false;
        var paper = 5;

        function print() {
            // underlying printer mechanics
            if (turnedOn) {
                if (paper > 0) {
                    console.log('printing page...');
                    paper -= 1;
                } else {
                    console.log('ran out of paper');
                }                
            } else {
                console.log('please turn on the printer first');
            }
        }

        function turnOn() {            
            console.log('warm up');        
            console.log('check for paper');
            turnedOn = true;
        }

        function turnOff() {
            console.log('turn led off');
            turnedOn = false;
        }

        function getStatus() {
            console.log('printer status', {turnedOn: turnedOn, paper: paper});
        }

        return {
            // public + private states and behaviors
            print: print,
            turnOn: turnOn,
            turnOff: turnOff,
            getStatus: getStatus
        };
    }

    return {
        getInstance: function () {
            console.log(printerInstance);
            if (!printerInstance) {                
                printerInstance = create();
            }
            return printerInstance;
        }
    };

})();

// usage
// var officePrinter = printer.getInstance();