Remember, unlike a traditional server-side application, which responds to requests

with HTML, a REST-ful API responds with data, most of the time a JSON object.

To see how this works,

let's write a simple route that responds to a GET request with JSON.

To follow along with me, download the starter files from the link on this page.

Locate the project folder from the terminal and

run npm install, to install the project's dependencies.

Then open the starter files in your preferred text editor.

We're starting off with some standard files for a basic Express app.

Along with a file called records.js, and a file called data.json,

both of which we'll discuss very soon.

Right now, let's look at the app.js file,

which is where we'll begin writing our code.

Open up that file, and you'll see that we're importing express,

creating an express app, and listening on port 3000.

We'll begin by creating an Express GET route handler.

Recall that the Express function adds a bunch of methods to Node's HTTP server,

to make it easier for us to receive and respond to requests.

These Express methods include GET, POST, PUT, and DELETE.

We're creating a GET method.

The GET method takes two arguments.

The first argument is the route that we wanna handle.

Let's write some code that will respond to a request to a route called greetings.

So in quotes, we'll say '/greetings'.

The second argument is the callback function we want to run when this request

comes in, how we want to respond.

Recall that when a client, a browser, or some other application makes a get request

to this URL, Express will run the code inside of this callback function.

This callback function takes at least two arguments,

one representing the incoming request from the client, and

one representing the outgoing response from the server.

By convention, they're both typically shortened to req for

request, and res for response.

Recall that in a traditional server-side Express application,

you'd respond to a client request using the Express res.render function,

to render a template and send HTML back to the client.

So you might do something like this.

You'd say res.render('some_html_template').

But we don't wanna do that, because we're building a REST API.

So inside the callback function, we wanna send back JSON.

So to do that, we can use the JSON method available on the response object.

So we can say res.json.

And we can pass the JSON method an object, and

it will convert that object to JSON and send it to the client.

So let's pass the JSON method an object.

And this object can be a greeting, Hello World!

Now let's save and test this out.

Open up a terminal on your computer.

Or if you're using VS Code, open your integrated terminal by

selecting it from the menu or using the keyboard shortcut Ctrl+\.

Type npm start, to get the server running.

Recall that this project is using nodemon to run the server, so

we don't have to keep restarting.

See the teacher's notes if you need assistance installing nodemon.

As you can see from the message in the console,

our app should be running at local host 3000.

If we visit localhost:3000/greetings from a browser,

You can see that our API is sending JSON when we make a request.

The browser, by default, sends a GET request.

By visiting localhost:3000/greetings,

we're sending a GET request to the greetings route, which we've programmed in

our Express application to send back a JSON object containing a greeting.

You've written code that responds to JSON when a client makes

a request to an endpoint.

At a high level, that's really all there is to it.

You've written a very simple REST API.

If all you want is a REST API that returns a simple message, then congratulations,

you're done.

But we want a REST API that provides much more functionality.

We want to display, create, update, and delete quotes.

With this in mind, let's plan out our application and

start building our first routes.