Express

Tags: #◇Web Development #◇CCAPDEV #◇Express #◇Code Snippets #◇M4

◇Overview

Extracted notes for Express covering both theoretical and practical elements.

◇Key Definitions

What is Express? Express is a light-weight NodeJS framework that provides robust features for web and mobile applications
Installing Express Search for Express in the npm repository and follow the installation instructions From a terminal, navigate to your project directory Generate a package.json file through npm init Run the command npm install express or npm i express This will install express to that specific project.
Creating an Express App Create your first Express App Create a project folder Generate a package.json file Install Express Create an app.js file Require express inside app.js Create an instance of an Express app
Creating a Server Use your Express app instance to listen for requests app.listen([port]) app variable containing your express app instance .listen listen to requests, just like server.listen() port the port number you wish to listen to
Creating a Server Use your Express app instance to listen for requests app.listen(3000) app variable containing your express app instance .listen listen to requests, just like server.listen() port the port number you wish to listen to We are now currently listening to requests in port 3000

◇Code Implementation

The Request Listener
Use app.get() to listen to GET requests (more on GET & POST requests next meeting). 
Let’s write a GET request listener:
app.get([url], [callback]);
 .get
specifies that we are listening to GET requests
 url
the value of the request URL
 callback
the function performed when a GET request for a
certain URL is made

The Request Listener
Use app.get() to listen to GET requests (more on GET & POST requests next meeting). 
Let’s write a GET request listener:
app.get(‘/home’, function(req, res){ });
 .get
specifies that we are listening to GET requests
 url
the value of the request URL
 callback
the function performed when a GET request for a
certain URL is made

URL Routing
Let’s handle requests to our web application
app.get(‘/’, function(req, res){ });
Same as before, use the res object to reply to the request
res.write() and res.end()
or use express’ new method:
res.send()
For new response methods provided by express:
https://expressjs.com/en/guide/routing.html#response-methods

Route Paths
app.get([path], function (req, res) { ... });
The route path can be strings, string patterns, and even regular expressions

Route Paths
app.get(`/`, function (req, res) { ... });
This route path will match requests to the root route, /.

◇Syntax Breakdown

Ensure correct syntax for Express Pay attention to specific functions and declarations.

◇Complexity Analysis

Time Complexity: O(1) for typical operations unless looping. Space Complexity: O(1) generally.

◇References & Navigation

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• Related Notes: ◇Client Server Architecture