Javascript Global App Singleton

global-singleton.js

/**
* Creates a app object in the global scope
*/
function initAppSingleton() {
  global = global || window;
  if (!global.app) {
    global.app = {};
  }
  return global.app;
}

/**
 * Sets a property to the app singleton global
 * 
 * @param {[type]} propertyName  [description]
 * @param {[type]} propertyValue [description]
 */
export function setAppSingletonProperty(propertyName, propertyValue) {
  const app = initAppSingleton();
  app[propertyName] = propertyValue;
}

/**
 * Gets a property value from the global app.
 * If the property is not present runs the setterFunction to create a new value
 * 
 * @param  {[type]} propertyName   [description]
 * @param  {[type]} setterFunction [description]
 * @return {[type]}                [description]
 */
export function getAppSingletonProperty(propertyName, setterFunction) {
  const app = initAppSingleton();
  let propertyValue = app[propertyName];

  if (!propertyValue && setterFunction) {
    console.log(`new app singleton for ${propertyName}`);
    propertyValue = setterFunction.call();
    setAppSingletonProperty(propertyName, propertyValue);
  }

  console.log(`app singleton for ${propertyName}`, propertyValue);

  return propertyValue;
}