Node.js Tutorial 101: Create a Simple App

A CodeMix eLearning Tutorial

Implement a web service using Express. This server exposes an endpoint that returns a list of people in Star Wars movies.

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# Node.js 101: Create a Simple App

### 01

# Welcome to Node.js 101!

In this tutorial, we will implement a WebService using Express. This server will expose an endpoint which will return a list of people in Star Wars movies.

A new project `tutorial-node101` has been added to your workspace. If you want to create your own Node project, select `File > New > Project...` and choose `CodeMix > Node Project`.

### 02

# Adding Express as a Dependency

To work with a Node.js project, you first need to install the required Node modules including adding the `express` module.

1. Type `npm install express` in Terminal+
2. Press `Enter`

### 03

# Importing Express
In order to make use of Express, we need to import it first.
In Node.js, this is done by using `require`, so let's import Express:

`const express = require('express');`

### 04

# Starting the server
Now that we have a reference to Express, let's create the instance of the server. Please add the following line:

`const server = express();`

Next step is to tell the server to start listening for client requests and respond accordingly.
The `listen` method of an Express instance does this, we can specify the port where the server is going to listen and a callback that will be executed when the server is up and running.
The code below brings up the server and will notify when its ready to accept requests, let's add it:

```
const port = 3000;

server.listen(port, () => {
  console.log(`Example server listening on port ${port}!`)
});
```

### 05

# Create route
In order to actually respond to client requests, we need to create routes.
A route refers to how the server endpoints (URIs) respond to client requests.

The most common way to define routes in Express is by using a function with a request and response object.
You can use the send method of response object to send data to the client.

Besides creating the route, we also need to make it available externally. This
is done by using `exports`. Let's not go in to details about how `exports` works,
just keep in mind that every member in it will be available when importing this file.

The following code reflects everything explained above, let's add it:

```
exports.default = function peopleRoute(_, response) {
  response.send(''); // Return nothing
}
```

### 06

# Return proper data
Our newly created route is not that useful as it returns nothing.
So, as described earlier in the tutorial, we need to respond with a list of Star Wars characters.
This tutorial already includes this data in JSON format in `/src/data/people.json`, so all we need 
to do is to load this data to a variable, let's do so:

```
const peopleData = require('../data/people.json');
```

The client expects the response to be a JSON object with 2 properties:
- count: Which is the total count of available Star Wars people entries.
- results: The actual Star Wars entries

We need to create this response object and pass it to `respond.send` which will
automatically serialize to JSON before send it to the client:

```
const responseObject = {
  count: peopleData.length,
  results: peopleData
};

exports.default = function peopleRoute(_, response) {
  response.send(responseObject);
}
```

### 07

# Use route in server entry point

In order to actually make use of the newly created route,  we need to register it with the server instance.
Let's begin by importing our new route by adding the following line at the top:

`const peopleRoute = require('./routes/people').default;`

As we want to use our route to respond to GET requests, let's use server.get to register the route. The first parameter is the route to respond to and the second is the callback. Add the following line just before the call to `server.listen`:

`server.get('/people', peopleRoute);`

### 08

# Start server

The code is done, open up a Terminal+ tab and run:
`npm run server`

We can now go to `http://localhost:3000/people` and see the list of Star Wars people

### 09

# Nice Job!!!

You've finished the Node 101 tutorial. As you are learning Node.js, why not check out <Node.js School|https://nodeschool.io/#workshoppers> for good examples of challenges you may face.

You can also check the <a href='https://www.genuitec.com/elearning/' target='_blank'>Vue 101</a> tutorial to learn how to build a client that can consume this web service.