Routing in Express
Logging in Express with Middleware
You may see the word 'middleware' on the web, particularly with regards to express. Middleware is simply code that is executed anywhere between a request and a response.
In our Hello World app we are logging out the server port once it has started - that is it. We get no other information about requests or errors. We can use Middleware to achieve this.
Add the following to your app.js file:
// app.js
.
.
.
app.set('view engine', 'ejs');
// Middleware
app.use(function(req, res, next) {
console.log('%s request to %s from %s', req.method, req.path, req.ip);
next();
});
app.get('/', function(req, res) {
.
.
.
Let's go through this: After setting up the view engine for our app, we use a method of app called use. The argument of use is a callback, also known as our middleware. use tells Express to use our middleware.
In this example, we are simply logging out the request method ('GET'), the request path ('/') and the request IP ('127.0.0.1' - localhost). next() is a callback function used for the purpose of allowing the app to continue on to other processes once this middleware is done executing. You can think of the next() function as telling the app to "move on" to the next middleware. This is handy because every middleware function can specify when it is complete.
The order of these arguments is crucial: request is always first, response is always second and the callback is always third.
Routes with Patterns
We've already seen some basic routes in the introduction, but often, we want routes that are more general. Instead of writing the exact url, we can define url patterns.
By putting a colon before a string in our route, we can create routes with different variables, or parameters. These parameters are automatically pulled out for us by Express and can be accessed via the req.params object.
Try running the script below and navigate to http://localhost:3000/greet/Prima/Aulia
var express = require('express');
var app = express();
app.get('/', function(req, res) {
res.send('hello brian');
});
app.get("/greet/:name/:lastname", function(req, res) {
res.send("Hello " + req.params.name + " " + req.params.lastname);
});
app.get("/multiply/:x/:y", function(req, res) {
res.send("The answer is: " + (req.params.x * req.params.y));
});
app.get("/add/:x/:y", function(req, res) {
res.send("The answer is: " + (parseInt(req.params.x) + parseInt(req.params.y)));
});
app.listen(3000);
In addition to having routes where different portions of the URL are different paramaters, we can use the generic string of the URL in our route logic using the wildcard.
app.get("/add/*", function(req, res) {
var myParams = req.params[0].split("/")
var result = myParams.reduce(function(total, num) {
return total + parseInt(num)
}, 0);
res.send("The answer is " + result);
});
Navigate to a URL like http://localhost:3000/add/5/3/3/2/3 and you will get an answer.
Using a Router - Codealong
We've added routes using app.use previously, but there's a better alternative: using a router. A router is like a part of your Express application that just handles the way your app does routing. It's normally better to use this way of doing routes because this allows all your routes to be in their own file. This allows us to make applications more modular, and you won't have a more manageable app.js.
Basic router
var express = require('express');
var app = express();
var port = 3000;
var router = express.Router();
app.set('view engine', 'ejs');
Then we add our routes.
router.get('/', function(req, res) {
res.render('index', { header: 'index!'});
});
router.get('/contact', function(req, res) {
res.render('index', { header: 'contact!'});
});
router.get('/about', function(req, res) {
res.render('index', { header: 'about!'});
});
At the bottom of the page add:
app.use('/', router);
//and of course
app.listen(3000);
Our views/index.ejs file will be simple:
<h1><%= header %></h1>
Creating a router module
Let's move this router into another file to separate it from our app.js
$ mkdir config
$ touch config/routes.js
Inside this file we need to move all of our route handlers and at the end of the file, we need to export our router:
var router = express.Router();
router.get('/', function(req, res) {
res.render('index', { header: 'index!'});
});
router.get('/contact', function(req, res) {
res.render('index', { header: 'contact!'});
});
router.get('/about', function(req, res) {
res.render('index', { header: 'about!'});
});
module.exports = router;
Now inside our app.js, let's require this router at the top:
var router = require("./config/routes");
Your directory should look something like this
.
├── config
│ └── routes.js
├── index.js
├── node_modules
├── package.json
└── views
└── index.ejs