Tutorial by Examples

You will first need to create a directory, access it in your shell and install Express using npm by running npm install express --save Create a file and name it app.js and add the following code which creates a new Express server and adds one endpoint to it (/ping) with the app.get method: const e...

First create an express app: const express = require('express'); const app = express(); Then you can define routes like this: app.get('/someUri', function (req, res, next) {}) That structure works for all HTTP methods, and expects a path as the first argument, and a handler for that path, w...

To get info from the requesting url (notice that req is the request object in the handler function of routes). Consider this route definition /settings/:user_id and this particular example /settings/32135?field=name // get the full path req.originalUrl // => /settings/32135?field=name // get...

To make express web application modular use router factories: Module: // greet.js const express = require('express'); module.exports = function(options = {}) { // Router factory const router = express.Router(); router.get('/greet', (req, res, next) => { res.end(options....

Using a Template Engine The following code will setup Jade as template engine. (Note: Jade has been renamed to pug as of December 2015.) const express = require('express'); //Imports the express module const app = express(); //Creates an instance of the express module const PORT = 3000; //Ra...

var express = require('express'); var cors = require('cors'); // Use cors module for enable Cross-origin resource sharing var app = express(); app.use(cors()); // for all routes var port = process.env.PORT || 8080; app.get('/', function(req, res) { var info = { 'string_value...

When building a webserver with Express it's often required to serve a combination of dynamic content and static files. For example, you may have index.html and script.js which are static files kept in the file system. It is common to use folder named 'public' to have static files. In this case th...

One big problem is that valuable named routes is not supported by Express out of the box. Solution is to install supported third-party package, for example express-reverse: npm install express-reverse Plug it in your project: var app = require('express')(); require('express-reverse')(app); ...

Basic Error Handling By default, Express will look for an 'error' view in the /views directory to render. Simply create the 'error' view and place it in the views directory to handle errors. Errors are written with the error message, status and stack trace, for example: views/error.pug html bo...

Express passes a next callback to every route handler and middleware function that can be used to break logic for single routes across multiple handlers. Calling next() with no arguments tells express to continue to the next matching middleware or route handler. Calling next(err) with an error will ...

Basic docs can be found here app.get('/path/:id(\\d+)', function (req, res, next) { // please note: "next" is passed if (req.params.id == 0) // validate param return next(new Error('Id is 0')); // go to first Error handler, see below // Catch error on sync operation ...

app.use() and middleware can be used for "before" and a combination of the close and finish events can be used for "after". app.use(function (req, res, next) { function afterResponse() { res.removeListener('finish', afterResponse); res.removeListener('clos...

Just like you handle get requests in Express with app.get method, you can use app.post method to handle post requests. But before you can handle POST requests, you will need to use the body-parser middleware. It simply parses the body of POST, PUT, DELETE and other requests. Body-Parser middleware...

The following is an example for setting and reading cookies using the cookie-parser module: var express = require('express'); var cookieParser = require('cookie-parser'); // module for parsing cookies var app = express(); app.use(cookieParser()); app.get('/setcookie', function(req, res){ ...

In Express, you can define middlewares that can be used for checking requests or setting some headers in response. app.use(function(req, res, next){ }); // signature Example The following code adds user to the request object and pass the control to the next matching route. var express = req...

In Express, you can define unified error handler for handling errors occurred in application. Define then handler at the end of all routes and logic code. Example var express = require('express'); var app = express(); //GET /names/john app.get('/names/:name', function(req, res, next){ if...

Middleware functions are functions that have access to the request object (req), the response object (res), and the next middleware function in the application’s request-response cycle. Middleware functions can execute any code, make changes to res and req objects, end response cycle and call next ...

Here we create a basic hello world server using Express. Routes: '/' '/wiki' And for rest will give "404" , i.e. page not found. 'use strict'; const port = process.env.PORT || 3000; var app = require('express')(); app.listen(port); app.get('/',(req,res)=>res.send(...