Overview 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. The next middleware function is commonly denoted by a variable named next. Middleware functions can perform the following tasks: Execute any code. Make changes to the request and the response objects. End the request-response cycle. Call the next middleware in the stack. If the current middleware func

A template engine enables you to use static template files in your application. At runtime, the template engine replaces variables in a template file with actual values, and transforms the template into an HTML file sent to the client. This approach makes it easier to design an HTML page. Some popular template engines that work with Express are Pug, Mustache, and EJS. The Express application generator uses Pug as its default, but it also supports several others. See Template Engines (Express wi

Express is a routing and middleware web framework that has minimal functionality of its own: An Express application is essentially a series of middleware function calls. 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. The next middleware function is commonly denoted by a variable named next. Middleware functions can perform the following tasks: Execute any co

To serve static files such as images, CSS files, and JavaScript files, use the express.static built-in middleware function in Express. Pass the name of the directory that contains the static assets to the express.static middleware function to start serving the files directly. For example, use the following code to serve images, CSS files, and JavaScript files in a directory named public: app.use(express.static('public')); Now, you can load the files that are in the public directory: http://loc

Node.js vulnerabilities directly affect Express. Therefore keep a watch on Node.js vulnerabilities and make sure you are using the latest stable version of Node.js. The list below enumerates the Express vulnerabilities that were fixed in the specified version update. NOTE: If you believe you have discovered a security vulnerability in Express, please see Security Policies and Procedures. 4.x 4.11.1 Fixed root path disclosure vulnerability in express.static, res.sendfile, and res.sendFile 4.

Routing refers to the definition of application end points (URIs) and how they respond to client requests. For an introduction to routing, see Basic routing. The following code is an example of a very basic route. var express = require('express'); var app = express(); // respond with "hello world" when a GET request is made to the homepage app.get('/', function(req, res) { res.send('hello world'); }); Route methods A route method is derived from one of the HTTP methods, and is attached to a

router.use([path], [function, ...] function) Uses the specified middleware function or functions, with optional mount path path, that defaults to “/”. This method is similar to app.use(). A simple example and use case is described below. See app.use() for more information. Middleware is like a plumbing pipe: requests start at the first middleware function defined and work their way “down” the middleware stack processing for each path they match. var express = require('express'); var app = expre

router.route(path) Returns an instance of a single route which you can then use to handle HTTP verbs with optional middleware. Use router.route() to avoid duplicate route naming and thus typo errors. Building on the router.param() example above, the following code shows how to use router.route() to specify various HTTP method handlers. var router = express.Router(); router.param('user_id', function(req, res, next, id) { // sample user, would actually fetch from DB, etc... req.user = {

router.param(name, callback) Adds callback triggers to route parameters, where name is the name of the parameter and callback is the callback function. Although name is technically optional, using this method without it is deprecated starting with Express v4.11.0 (see below). The parameters of the callback function are: req, the request object. res, the response object. next, indicating the next middleware function. The value of the name parameter. The name of the parameter. Unlike app.pa

router.METHOD(path, [callback, ...] callback) The router.METHOD() methods provide the routing functionality in Express, where METHOD is one of the HTTP methods, such as GET, PUT, POST, and so on, in lowercase. Thus, the actual methods are router.get(), router.post(), router.put(), and so on. You can provide multiple callbacks, and all are treated equally, and behave just like middleware, except that these callbacks may invoke next('route') to bypass the remaining route callback(s). You can use