Express JS

Introduction

• Developed by TJ Holowaychuk in November 2010.
• Is a web application framework for Node.js.
• Free and open-source software.
• Licensed under MIT.

Features

• Facilitates the rapid development.
• Allow to set up middleware to respond to HTTP requests.
• Defines a routing table.
• Allows to dynamically render HTML pages.

Environment Setup

• Install node.js and npm

• Install express module by npm command

--save: Package will appear in your dependencies.

Express Routing

• Refers how an application responds to a client request to an endpoint.
• Each route can have one or more handler functions.

app.METHOD(PATH,HANDLER)

Express JS URL Binding

✦req.params used to read the bind values(name,age).
✦regular expression also used to name parameter.

Express JS Middleware

• Express is middleware web framework that has minimal functionality of its own.
• An Express application is essentially a series of middleware function calls.
• Middleware functions access to the request object, the response object, and the next middleware function.

✦app.use() used to Mounts the middleware function or mount to a specified path,the middleware function is executed when the base path matches.

✦The order you place your middleware is very important. Everything will happen in the order that they appear.

Express Router

✦Express router is a class which helps us to create router handlers. By router handler i mean to not just providing routing to our app but also can extend this routing to handle validation, handle 404 or other errors etc.

Express JS Templating

✦Template engine allows you to use static template files in your application.

✦Some popular template engines that work with Express are Pug, Mustache, and EJS.

✦Here, we'll use Pug.

Pug

✦Is a templating engine for express.

✦Earlier it was called Jade.

✦npm command is used to install this package. 

Express Static Files

⊿Are files that clients use as they are from the server.
⊿Files such as images, CSS files, and JavaScript files are served using express.static middleware function.
⊿Express looks up the files relative to the static directory.

app.use(express.static(__dirname+'public'));

⊿We can also set multiple static directories.