Configuration Singleton Example - JavaScript

configuration.js

/**
 * http://robdodson.me/javascript-design-patterns-singleton/
 * http://addyosmani.com/resources/essentialjsdesignpatterns/book/#singletonpatternjavascript
 */

var Configuration = (function () {

  // Instance stores a reference to the Singleton
  var instance;

  function init() {

    // Singleton

    // Private methods and variables
    function loadConfig(){
        console.log( "Loading Config ..." );
    }

    function saveConfig(){
        console.log( "Saving Config ..." );
    }

    function createConfig(){
        console.log( "Creating Config ..." );
    }

    var refreshInterval = 999; //Set with a default value

    loadConfig();

    return {

      // Public methods and variables
      getRefreshInterval: function () {
        console.log( "Getting Refresh Interval" );
        return refreshInterval;
      },

      setRefreshInterval: function (refreshIntervalParam) {
        console.log( "Setting Refresh Interval" );

        refreshInterval = refreshIntervalParam;

        saveConfig();
      }

      /**
       * @todo add the other getters and setters
       */

    };

  };

  return {

    // Get the Singleton instance if one exists
    // or create one if it doesn't
    getInstance: function () {

      if ( !instance ) {
        instance = init();
      }

      return instance;
    }

  };

})();

// Usage:

var singleA = Configuration.getInstance();
var singleB = Configuration.getInstance();

console.log( "Are the two instances the same? " + (singleA === singleB) ); // true

Configuration.getInstance().setRefreshInterval(2000);
console.log("Refresh Interval is: " + Configuration.getInstance().getRefreshInterval());