Express.js Routing and Request Handling

Request and Response Objects

• The req object represents the HTTP request and contains properties for the request query string, parameters, body, HTTP headers, etc.
• The res object represents the HTTP response that the Express app sends when it receives an HTTP request.
• The res.send() function takes an object as input and sends it to the requesting client.

Routing in Express

• Web frameworks provide resources such as HTML pages, scripts, images, etc. at different routes.
• Routes are defined using the app.method(path, handler) function,
• METHOD can be any HTTP verb like get, set, put, or delete. It defines what type of request the route should handle.
• path is the route at which the request will run.
• handler is a callback function that executes when a matching request type is found on the relevant route.
• The app.all(path, handler) method can handle all types of HTTP methods at a particular route using the same function.

Middleware

• Middleware is a function that has access to the request and response objects, and the next middleware in the stack.
• It can be used to perform tasks such as logging, authentication, and authorization.
• It is generally used for defining middleware, which we'll discuss in the middleware.

Templating with Pug

• To use Pug with Express, install it with npm install --save pug.
• Set the view engine to pug using app.set('view engine', 'pug') and the views directory using app.set('views','./views').
• Pug simplifies HTML markup, removes the need for closing tags, and provides a cleaner syntax for defining classes and IDs using . and #.
• Pug enables a more efficient way of writing code.
• Pug is capable of doing more than simplifying HTML markup.

Pug Features

• Simple Tags: Tags are nested according to their indentation. Pug provides mechanisms to write them using the indentation, removing the need for explicit closing tags.
• Comments: Pug uses the same syntax as JavaScript (//) for creating comments, which are converted to HTML comments (<!-- -->).
• Attributes: To define attributes, use a comma-separated list of attributes in parentheses. The attributes can be accessed using the #{} operator in the template.

Rendering Pug Templates

• Rendering from String: The render function from the pug module compiles a Pug template string and its data into an HTML string.
• compileFile Function: Compiles a Pug template from a file to a function, which can be rendered multiple times with different locals.
• renderFile Function: Compiles a Pug template from a file and renders it with locals to an HTML string.

HTTP Methods

• GET: Requests a representation of the specified resource. Should only retrieve data and have no other side effects.
• POST: Requests the server to accept the data enclosed in the request as a new object/entity of the resource identified by the URI.
• PUT: Requests the server to accept the data enclosed in the request as a modification to an existing object identified by the URI. If it doesn't exist, it should create one.
• DELETE: Requests the server to delete the specified resource.

RESTful APIs

• RESTful APIs use URIs and HTTP methods to represent resources and operations on them.
• The table below summarizes how HTTP verbs should be used and how URIs should be named:

Creating a Movies API

• You can create a RESTful interface to create a new movie resource using a route defined with the router.post() method in the Express.
• You can test the route by using the curl command with the -X POST option, providing the data as a query string in the URL.
• To update an existing resource, you can use the PUT method with the id of the resource in the URI.
• To delete a resource, you can use the DELETE method with the id of the resource in the URI.

This quiz focuses on the foundational concepts of routing and request-response handling in Express.js. It covers the roles of the req and res objects, the definition of routes, and the use of middleware. Test your knowledge on how these components work together in a Node.js web application.