An Example of Why Promises and Generators are Important

SupplementToRedemptionFromCallbackHell

// An Example of Why Promises and Generators are Important
// Based on this awesome video: https://www.youtube.com/watch?v=hf1T_AONQJU
// You can just copy and paste this code into your console to see it in action

var App = function App(){

  // Named anonymous functions for clear picture
  // of the call stack in the error stack trace
  this.asyncError = function myAsynchronousError(){
    throw new Error('Asynchronous error');
  };

  this.syncError = function mySynchronousError(){
    throw new Error('Synchronous error');
  };

  // Capitlized instead of camelCased to keep the name clear
  this.Return = function Return(){
    return arguments.callee;
  };

};

(function global(){
  var app = new App();

  // Synchronous Return
  // Able to access the returned value 
  // of app.Return which is app.Return.toString()
  console.log(app.Return());

  // Asynchronous Return
  // The returned value cannot be accessed. The value of 1 is printed
  // when setTimeout is succesfully called.
  console.log(setTimeout(app.Return, 1000));

  // Asynchronous Error
  // The callstack does not have the context of
  // the App instance, the global anonymous 
  // boot function, or the anonymous JS function
  // at the root of the program.
  /*
    Uncaught Error: Asynchronous error index.html:7
    myAsynchronousError
  */
  setTimeout(app.asyncError, 1000);

  // Synchronous Error
  // The throw statement gives you the entire call stack:
  /*
    Uncaught Error: Synchronous error index.html:11
    mySynchronousError index.html:11
    global index.html:27
    (anonymous function)
  */
  app.syncError();

}());