// Functions have access to variables defined in the same scope
                              
                            
                          
                          

                            

                              var foo = "hello";
                            
                          
                          

                            

                              var sayHello = function() {
                            
                          
                          

                            

                                console.log( foo );
                            
                          
                          

                            

                              };
                            
                          
                          

                            

                               
                            
                          
                          

                            

                              sayHello(); // "hello"
                            
                          
                          

                            

                              console.log( foo ); // "hello"
                            
                          
                        

                          

                            

                              
                                // Code outside the scope in which a variable was defined does not have access to the variable
                              
                            
                          
                          

                            

                              var sayHello = function() {
                            
                          
                          

                            

                                var foo = "hello";
                            
                          
                          

                            

                                console.log( foo );
                            
                          
                          

                            

                              };
                            
                          
                          

                            

                               
                            
                          
                          

                            

                              sayHello(); // hello
                            
                          
                          

                            

                               
                            
                          
                          

                            

                              console.log( foo ); // undefined
                            
                          
                        

                          

                            

                              
                                // Variables with the same name can exist in different scopes with different values
                              
                            
                          
                          

                            

                              var foo = "world";
                            
                          
                          

                            

                               
                            
                          
                          

                            

                              var sayHello = function() {
                            
                          
                          

                            

                                var foo = "hello";
                            
                          
                          

                            

                                console.log( foo );
                            
                          
                          

                            

                              };
                            
                          
                          

                            

                               
                            
                          
                          

                            

                              sayHello();         // logs "hello"
                            
                          
                          

                            

                              console.log( foo ); // logs "world"
                            
                          
                        

                          

                            

                              
                                // Functions can see changes in variable values after the function is defined
                              
                            
                          
                          

                            

                              var myFunction = function() {
                            
                          
                          

                            

                                  var foo = "hello";
                            
                          
                          

                            

                                  var myFn = function() {
                            
                          
                          

                            

                                      console.log( foo );
                            
                          
                          

                            

                                  };
                            
                          
                          

                            

                                  foo = "world";
                            
                          
                          

                            

                                  return myFn;
                            
                          
                          

                            

                              };
                            
                          
                          

                            

                               
                            
                          
                          

                            

                              var f = myFunction();
                            
                          
                          

                            

                              f(); // "world"
                            
                          
                        

                          

                            

                              
                                // Scope insanity
                              
                            
                          
                          

                            

                              
                                // a self-executing anonymous function
                              
                            
                          
                          

                            

                              (function() {
                            
                          
                          

                            

                                var baz = 1;
                            
                          
                          

                            

                                var bim = function() {
                            
                          
                          

                            

                                  alert( baz );
                            
                          
                          

                            

                                };
                            
                          
                          

                            

                               
                            
                          
                          

                            

                                bar = function() {
                            
                          
                          

                            

                                  alert( baz );
                            
                          
                          

                            

                                };
                            
                          
                          

                            

                               
                            
                          
                          

                            

                              })();
                            
                          
                          

                            

                               
                            
                          
                          

                            

                              
                                // baz is not defined outside of the function
                              
                            
                          
                          

                            

                              console.log( baz );
                            
                          
                          

                            

                               
                            
                          
                          

                            

                              
                                // bar is defined outside of the anonymous function
                              
                            
                          
                          

                            

                              
                                // because it wasn't declared with var; furthermore,
                              
                            
                          
                          

                            

                              
                                // because it was defined in the same scope as baz,
                              
                            
                          
                          

                            

                              
                                // it has access to baz even though other code
                              
                            
                          
                          

                            

                              
                                // outside of the function does not
                              
                            
                          
                          

                            

                              bar();
                            
                          
                          

                            

                               
                            
                          
                          

                            

                              
                                // bim is not defined outside of the anonymous function,
                              
                            
                          
                          

                            

                              
                                // so this will result in an error
                              
                            
                          
                          

                            

                              bim();