Module 2 - Server-Side Routing with Express

Objectives

Understanding Express Routing

Routing refers to determining how an application responds to a client request to a particular endpoint, which is a URI (or path) and a specific HTTP request method (GET, POST, etc.). Each route can have one or more handler functions, which are executed when the route is matched.

Express routing enables us to:

Organize our application based on URL paths and HTTP methods
Execute specific code based on the client's request
Separate concerns by breaking the application into smaller, more manageable parts
Create a modular API with clear, predictable endpoints

Route Methods in Express

Express provides methods that correspond to HTTP methods. The most common ones are:

server.get() - Handle GET requests (retrieve data)
server.post() - Handle POST requests (create new data)
server.put() - Handle PUT requests (update existing data)
server.delete() - Handle DELETE requests (remove data)

Each method takes two arguments: the route path and the callback function(s) that handle the request and response.

Basic Routing Example

Let's look at a basic example of routing in action. First, to make our Express application respond to GET requests on different URLs, add the following endpoints:

// this request handler executes when making a GET request to /about
server.get('/about', (req, res) => {
    res.status(200).send('<h1>About Us</h1>');
});

// this request handler executes when making a GET request to /contact
server.get('/contact', (req, res) => {
    res.status(200).send('<h1>Contact Form</h1>');
});

Two things to note:

We use the same HTTP Method on both endpoints, but Express looks at the URL and executes the corresponding request handler.
We can return a string with valid HTML!

Open a browser and navigate to the /about and /contact routes. The appropriate route handler will execute.

HTTP Status Codes

When responding to requests, it's important to use the appropriate HTTP status codes:

200 (OK) - Standard response for successful HTTP requests, typically used for GET and PUT
201 (Created) - The request has been fulfilled and resulted in a new resource being created, typically used for POST
204 (No Content) - The server successfully processed the request, but is not returning any content, typically used for DELETE
400 (Bad Request) - The server cannot process the request due to a client error
404 (Not Found) - The requested resource could not be found
500 (Internal Server Error) - A generic error message when the server encounters an unexpected condition

Follow Along

Let's write endpoints that execute different request handlers on the same URL by changing the HTTP method.

First, add a POST endpoint:

// this request handler executes when making a POST request to /hobbits
server.post('/hobbits', (req, res) => {
    res.status(201).json({ url: '/hobbits', operation: 'POST' });
});

Next, add a PUT endpoint:

// this request handler executes when making a PUT request to /hobbits
server.put('/hobbits', (req, res) => {
    res.status(200).json({ url: '/hobbits', operation: 'PUT' });
});

Finally, add a DELETE endpoint:

// this request handler executes when making a DELETE request to /hobbits
server.delete('/hobbits', (req, res) => {
    res.status(204);
});

Note the different HTTP status codes we're using:

201 (Created) for successful POST operations
200 (OK) for successful PUT operations
204 (No Content) for successful DELETE operations

You may have noticed that we are not reading any data from the request, as that is something we'll learn later in the module. We are about to learn how to use a tool called Postman to test our POST, PUT, and DELETE endpoints.

Testing API Endpoints

While you can test GET requests easily in a browser, other HTTP methods (POST, PUT, DELETE) require specialized tools. Some popular options include:

Postman - A powerful GUI tool for API testing
Insomnia - Another GUI-based REST client
curl - Command-line tool for transferring data with URLs
HTTPie - Human-friendly command-line HTTP client

These tools allow you to craft custom HTTP requests with specific headers, body content, and parameters.

Challenge

Add endpoints to handle POST, PUT, and DELETE for the /users route. Return a JSON response similar to what we did in the code-along.

Try implementing the following functionality:

POST to /users - Return a 201 status code and a JSON object with information about the operation
PUT to /users - Return a 200 status code and relevant information about the update
DELETE to /users - Return a 204 status code to indicate successful deletion with no content

Test your endpoints using Postman or another API testing tool.

Module 2 - Server-Side Routing with Express

Objectives

Understanding Express Routing

Route Methods in Express

Basic Routing Example

HTTP Status Codes

Follow Along

Testing API Endpoints

Challenge

Guided Project

Project Resources

Starter Repository

Solution Repository

Optional Tools

Important Notes

Assignment

Project Resources

Starter Repository

Solution Repository