iife returned function not working correctly

Question

I'm trying to create a module, and I'm trying to use the correct design. I saw this library, and they had a iife returning the function that's a module. I tried doing that like this:

(function() {
  function MyModule() {
    var something = 'something';
    this.log = log();
  }

  MyModule.prototype.alert = function() {
    alert(this.something);
  };

  function log() {
    console.log('hello');
  }

  return MyModule;
})();

var module1 = new MyModule();

But I get the following error:

Uncaught ReferenceError: MyModule is not defined

Here's the relevant copied code:

• Start
• Main Function
• End / return

What am i doing wrong, and how can I fix it?

Answer 1

MyModule is staying inside the IIFE clousure so it wont be visible from code outside. Assign the result of the IIFE to a MyModule variable

Also, you probably meant to assign the log function to the MyModule being constructed, and not its result (undefined)

And finally, the fact that you declare a variable called something in the constructor does not assign it as a property of the object being constructed. If you wanted something to be private, you have to declare the alert method inside the clousure of the constructor:

var MyModule = (function() {
  function MyModule() {
    var something = 'something';
    this.log = log;
    // this.log = log();

    this.alert = function() {
        alert(something);
    };
  }

  //MyModule.prototype.alert = function() {
  //    alert(this.something);
  //};

  function log() {
    console.log('hello');
  }

  return MyModule;
})();

var module1 = new MyModule();

module1.alert(); // Alerts 'something'
module1.log(); // Logs 'hello'

To really understand JavaScript, forget about classes, learn about prototypes and functions in general, specially clousures.

Watch this brilliant conference by Douglas Crockford to get it right.