// Modules should be Immediately-Invoked-Function-Expressions (IIFE) to allow for private scopes
// return an object instead of a function
var ChangeAttribute = (function() {
  var content = 'content'  // private variable

  var changeHTML = function() {
    var element = document.getElementById('attribute-to-change');
    element.innerHTML = content;
  }

  return { // here begin the magic ^^, when you return function.
    callChangeHTML: function() {  // became public variable, but onlly if you call callChangeHTML!
      changeHTML();
      console.log(content);
    }
  };

})();

ChangeAttribute.callChangeHTML();      // Outputs: 'content'
console.log(ChangeAttribute.content);  // undefined