A Simple API

Remember, unlike a traditional server-side application, which responds to requests 0:00 with HTML, a REST-ful API responds with data, most of the time a JSON object. 0:05 To see how this works, 0:09 let's write a simple route that responds to a GET request with JSON. 0:11 To follow along with me, download the starter files from the link on this page. 0:15 Locate the project folder from the terminal and 0:20 run npm install, to install the project's dependencies. 0:22 Then open the starter files in your preferred text editor. 0:26 We're starting off with some standard files for a basic Express app. 0:29 Along with a file called records.js, and a file called data.json, 0:33 both of which we'll discuss very soon. 0:37 Right now, let's look at the app.js file, 0:39 which is where we'll begin writing our code. 0:42 Open up that file, and you'll see that we're importing express, 0:44 creating an express app, and listening on port 3000. 0:48 We'll begin by creating an Express GET route handler. 0:51 Recall that the Express function adds a bunch of methods to Node's HTTP server, 0:55 to make it easier for us to receive and respond to requests. 1:00 These Express methods include GET, POST, PUT, and DELETE. 1:04 We're creating a GET method. 1:08 The GET method takes two arguments. 1:12 The first argument is the route that we wanna handle. 1:14 Let's write some code that will respond to a request to a route called greetings. 1:16 So in quotes, we'll say '/greetings'. 1:20 The second argument is the callback function we want to run when this request 1:23 comes in, how we want to respond. 1:28 Recall that when a client, a browser, or some other application makes a get request 1:33 to this URL, Express will run the code inside of this callback function. 1:37 This callback function takes at least two arguments, 1:43 one representing the incoming request from the client, and 1:46 one representing the outgoing response from the server. 1:49 By convention, they're both typically shortened to req for 1:52 request, and res for response. 1:57 Recall that in a traditional server-side Express application, 1:59 you'd respond to a client request using the Express res.render function, 2:03 to render a template and send HTML back to the client. 2:08 So you might do something like this. 2:11 You'd say res.render('some_html_template'). 2:13 But we don't wanna do that, because we're building a REST API. 2:19 So inside the callback function, we wanna send back JSON. 2:22 So to do that, we can use the JSON method available on the response object. 2:25 So we can say res.json. 2:30 And we can pass the JSON method an object, and 2:33 it will convert that object to JSON and send it to the client. 2:36 So let's pass the JSON method an object. 2:41 And this object can be a greeting, Hello World! 2:45 Now let's save and test this out. 2:49 Open up a terminal on your computer. 2:52 Or if you're using VS Code, open your integrated terminal by 2:54 selecting it from the menu or using the keyboard shortcut Ctrl+\. 2:58 Type npm start, to get the server running. 3:03 Recall that this project is using nodemon to run the server, so 3:07 we don't have to keep restarting. 3:10 See the teacher's notes if you need assistance installing nodemon. 3:12 As you can see from the message in the console, 3:16 our app should be running at local host 3000. 3:18 If we visit localhost:3000/greetings from a browser, 3:21 You can see that our API is sending JSON when we make a request. 3:28 The browser, by default, sends a GET request. 3:32 By visiting localhost:3000/greetings, 3:35 we're sending a GET request to the greetings route, which we've programmed in 3:38 our Express application to send back a JSON object containing a greeting. 3:43 You've written code that responds to JSON when a client makes 3:47 a request to an endpoint. 3:50 At a high level, that's really all there is to it. 3:51 You've written a very simple REST API. 3:54 If all you want is a REST API that returns a simple message, then congratulations, 3:56 you're done. 4:01 But we want a REST API that provides much more functionality. 4:02 We want to display, create, update, and delete quotes. 4:05 With this in mind, let's plan out our application and 4:08 start building our first routes. 4:11