What is Express?

Powerful, extensible framework for web apps
Similar to Sinatra / Rails
Middleware based
Great community support
Lets you focus on your website instead of boilerplate

Is it Production Ready?

Getting Started

Install Express

npm install -g express

Initialize your application with whatever extras you'd like

express --sessions --css less --ejs myapp

Install your dependencies

cd myapp && npm install

All finished!

node myapp

Cool... but what just happened?

Basic Structure of an App

package.json

{
  "name": "myapp",
  "version": "0.0.1",
  "private": true,
  "scripts": {
    "start": "node app.js"
  },
  "dependencies": {
    "express": "3.4.0",
    "ejs": "*",
    "less-middleware": "*"
  }
}

app.js

Everything is

Middleware

Routes - user.js

/*
 * GET users listing.
 */

exports.list = function(req, res){
  res.send("respond with a resource");
};

Routes - index.js

/*
 * GET home page.
 */

exports.index = function(req, res){
  res.render('index', { title: 'Express' });
};

<!DOCTYPE html>
<html>
  <head>
    <title><%= title %></title>
    <link rel='stylesheet' href='/stylesheets/style.css' />
  </head>
  <body>
    <h1><%= title %></h1>
    <p>Welcome to <%= title %></p>
  </body>
</html>

Setting Up Your

Express App

App-Level Configuration

app.set('title', 'Javascript Everywhere');

app.get('title');
// => "Javascript Everywhere"

app.enable('trust proxy');
app.get('trust proxy');
// => true
app.disable('trust proxy');app.get('trust proxy');// => false

Environment-Specific Config.

// all environments
app.configure(function(){
  app.set('title', 'Fancy Web App');
})

// development only
app.configure('development', function(){
  app.set('db uri', 'localhost/dev');
})

// production only
app.configure('production', function(){
  app.set('db uri', '255.255.255.255/prod');
})

View Engines

Initialize your view engine (in this case - EJS)

app.set('view engine', 'ejs');

Equivalent to:

app.engine('ejs', require('ejs').__express);

Writing Your Own

Middleware

Basic Middleware (CSRF Check)

// Check that a unique token is present in a request
function checkForCsrf(req,res,next) {
    //use param, e.g., if token is valid proceed with next();
    if(req.param("_csrf") === req.csrfToken) {
        next();
    } else {
        next("Invalid CSRF token")
    }
});

Error Handling Middleware

Takes four arguments - err, req, res, next
Should appear low in your middleware stack

function(err, req, res, next){
    console.error(err.stack);
    res.send(500, 'Something broke!');
};

Using Middleware in Your App

app.use(function(req,res,next) { // checkForCsrf
    //use param, e.g., if token is valid proceed with next();
    if(req.param("_csrf") === req.csrfToken) {
        next();
    } else {
        next("Invalid CSRF token")
    }
});

Request Handling /

View Routing

Remember - it's just middleware!

Basic Request Handling

Send JSON string for GET request:

app.get("/json", function(req, res) {
    res.json({
        x: "A variable!",
        y: 1,
        z: true
    });
});

Send 404 when no document is found:

app.get("/documents/:id", function(req, res) {
    // Nothing found!
    res.send(404);
});

Thanks!

Questions?

Logan Fuller

@Logan_Fuller