Intro to Express

#HarvestJS

Special Thanks to:

Express Request Handling

Executed in order
Callbacks can do 1 of 2 things

Handle the response
Pass control on

This is the basis for middleware

Middleware

Just functions that handle requests
Handlers are executed in order
Handlers can be "stacked"

Route Callback

function(req, res) { //code }

Middleware Callback

function(req, res, next) { //code }

Control is passed along using next();

Route Callback

        app.get('/route', function(req, res) {

          //code

});

Middleware Callback

        app.use(function(req, res, next) {

          //code

});

Every request goes through the middleware

Examples

Authentication
Authorization
Static files
Body parsing (forms)
Cookie parsing

Authentication Example

app.use(function(req, res, next) {   if ( ! loggedIn ) {     res.end('You are not authorized');   } else {     next();   } });

Show message if not logged in
Send request on if they are

Middleware

Can also modify the request

app.use(function(req, res, next) {  req.user.name = 'John Lithgow';  req.user.career = 'actor';  req.user.age = '67';  next();});

Will append user to the request object
req.user will be available in subsequent handlers

Order Matters

app.use(app.router);app.use(express.static(path.join(__dirname, 'public')));
app.use(function(req, res, next) {  res.end(404, 'Not found');});
app.get('/', function(req, res) {  res.send('Hello World');});

app.router is used for route handling
Routes are injected before the 404 Middleware