Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications.

express

Node.js is a platform built on Chrome's JavaScript runtime for easily building fast, scalable network applications. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices.

Node.js

Express is a well-known and supported framework for Node web applications. It provides a lot of excellent functionality to process requests, interact with other APIs, handle authentication and return appropriate requests for any client.

This course will look at providing an API for a specific application but will explore concepts that will be helpful in building a wide variety of applications.

In this lesson, we set-up an Express application and have it send a test response. We then test that the server is working using an API client, in this case Insomnia. We'll also install and setup nodemon so our server will reload every time our files change making development much faster.

Set up Express to Automatically Reload on Save with nodemon

In this lesson we'll introduce our Catchphrase app and use our Express API to serve the image URL. We'll add our custom client side fetch call and deal with CORS issues created by serving our API and application from different origins.

Return JSON from Express and Handle CORS Errors 

In this lesson we will look at serving static files using the static helper provided by Express.

We'll then use the file system module in Node to read the contents of our static directory, select a random file and send the path back to our client.


Serve a random static file with Express

By default, Express doesn't parse JSON passed in the request body. In fact, the request body is seen as null by Express.

We need to add middleware to allow Express to be able to access the information passed in. In the past, we've had to lean on other libraries such as body-parser. As of version 4.17, Express now comes bundled with it's own JSON middleware.

We will use that middleware in this lesson, build some logic and send a response back to our client.

Parse and Process JSON with Express

Express provides a straightforward workflow to add functionality between the request and the response.

In this space your application can check the request, query other APIs and build up the response in parts before sending the final response.

In this lesson, we'll add an authenication middleware that will check for a specific header and confirm that it has the correct value. If either of these tests fail then the middleware will send an early response with a 401 status.

Create Custom Middleware for Authentication in Express

egghead

Create custom middleware for authentication in Express

In this lesson, we'll look at how to handle errors in syncronous and asyncronous request handler functions. 

We'll also look at custom error middleware that allows for better control over how we return errors to our client based on whether we are in a production or development environment.

Handle Syncronous and Asyncronous Errors in Express

One way to secure API routes is by using JSON Web Tokens (JWTs) which are passed with each request and checked before a lesson is returned. To do this, you need an OAuth server to provide the signing and authentication of these tokens. Auth0 provides this for free for up to 7,000 users. 

In this lesson, we'll configure Auth0 and gather the details we need to be able to secure our API routes.

Configure an Auth0 API Authentication to Use with Your Server

Sending a JSON Web Token is one way to valid your identity as a user of an API or service. In this lesson, we will see how to add an Express middleware which will check for a valid JWT and return a 401 Unauthorized error if not.

Add Middleware to Validate a JSON Web Token (JWT)

In this lesson, we will use Auth0 to generate a JWT that we can use to validate future requests to our server.

We will then return that token and test that it works when authenicated by our middleware.

During the lesson, we'll also briefly look at a strategy to keep your credentials out of source control using a .gitignore file. 

Get a JWT From Auth0 in Express to Be Used in Authentication

In this lesson, we'll add some middleware to support the upload of files to our Express server. 

We'll test for validity, handle errors and move the file to our storage directory.

Finally, we'll test our route using our API client.

Building an API with Express

Kevin Cunningham

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