So far, we have an Express app that runs, but can't do much more than that.

To accept JSON data coming into our routes,

we'll need to introduce some middleware to our Express application.

While we could write the logic to parse the JSON in the incoming request

ourselves, someone has already written a module that will do this for

us called body-parser.

Let's install back here in the terminal and save it to our package.json file.

npm install --save

body-parser@~1.15 This will save

this specific version to our package.json file with the latest patch release.

To use this module,

we'll switch back to the app.js file and

enter, var jsonParser

= require("body-parser").json

Underneath the Express dependency body-parser contains a number of

parsers to help you manage HTTP requests.

But we only need the JSON parser for this project.

jsonParser is a function that will return middleware that we can add to our app.

On the app object, we can call the use method and

use jsonParser's returned middleware.

When the app receives a request, this middleware will parse the request

body as JSON and make it accessible from the request's body property.

This is similar to how we passed in the my message property between middleware.

Let's take a look at this in action to see it a little more clearly.

First, we're going to write some middleware before the jsonParser is added.

This checks to see if the request body object has the property named body.

If it does.

It logs out, the sky is, and

then the color from the incoming JSON.

If it doesn't, let's log out.

There is no body property on the request.

We're expecting that it doesn't,

because the jsonParser hasn't been able to get his hands on the request yet.

Let's add the exact same middleware after the JSON parser is introduced to see if

there's a difference.

This will work, but let's refactor it slightly.

We've just added the exact same lines of code twice in our application,

which is a red flag that we could do something better.

Let's assign our middleware function to the variable jsonCheck.

Then we can use it with our before and after checks like this.

That looks so much cleaner.

Remember to save the application.

Move over to the terminal and start the server.

In Postman, let's make a POST request to our API.

Choose POST from the dropdown.

Make sure the url is localhost:3000.

Click on Body.

This is where we're going to put the JSON in the body of our request.

Select raw and make sure that JSON, application/json,

Is selected here in the Content-Type dropdown.

In this text area here, we can enter the JSON we want to send.

Let's put color: blue.

Hit Send, and we'll see the same error we did with GET requests we made earlier.

But that's okay, we haven't defined any routes yet.

Let's go back to the terminal and see what we have there.

When the first middleware is hit, the JSON is not parsed yet, but

the second shows that we had access to the data.

This is after the JSON parser was introduced to the app.

Great.

Let's stop the server and delete the middleware we just created.

Leaving only the JSON parser behind.

In the next video, we'll start building the routes for the API.