Simple Local Rest Server

Installing Node.js

Navigate to the Node.js downloads page found here and download the correct file for your operating systems.

For Windows

For those on Windows, just follow the install wizard. Once Node is installed you can check your install by opening PowerShell (or another commandline tool if you prefer) and running the commands: node -v and npm -v. These commands should both produce a version number if successfully installed.

For Mac

For those on Mac, you may wish to install through Homebrew instead as it saves you some effort in getting ready to start development.

You will need Xcode from the Apple App Store and Homebrew which can be installed via commandline:

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

Just follow the prompts to finish installing Homebrew.

Once you have Homebrew installed, you can can install Node with the following command: brew install node. Once Node is installed, you can check your installation by running the command node -v, if you have successfully installed node you should see a version number in your commandline. You should run a similar command to ensure the Node Package Manager (NPM) is installed correctly, the command is: npm -v. Once again, if NPM has been successfully installed, you should see a version number.

Creating a Node project

Using NPM, we can follow a commandline wizard to create a package.json file, which lets us install dependencies, run all our tests with a single command and more. This command is: npm init.

Create a folder for your project, enter the folder and then run npm init. The first prompt is for your package (read: application) name, you will then be prompted with a number of other fields, you can just keep hitting enter to get through it! Before the package file is generated, you will be asked to confirm that it is correct.

Once you have successfully generated your package file, the next step is to create your main JavaScript file. Make sure to use the same name as you supplied in your package file, it is index.js by default.

For Mac

If you are fond of the commandline and using a non-windows machine, you can likely use the touch command. This command creates an empty file for you, the following command will produce an empty file called index.js: touch index.js.

Setting up an Express Node server

The Express framework for Node.js is a fast, small and flexible framework that provides a robust set of features for web and mobile applications, using this we can quickly set-up a RESTful API server.

Installing Express

To install Express, navigate to the root-folder of your application and run the command: npm install express --save-dev. The --save-dev flag means that the package will be added to our package file, if all of your packages are added to the package file then you can install all your dependencies with one command: npm install. This must be ran on the same level as your package.json file.

Starting a server

To get up and running, we will write a very basic server using GET as the HTTP method.

Note: You can use app.post for the post method, and so on.

// our dependencies

const express = require('express');

const app = express();

// from top level path e.g. localhost:3000, this response will be sent

app.get('/', (request, response) => response.send('Hello World'));

// set the server to listen on port 3000

app.listen(3000, () => console.log('Listening on port 3000'));

If you add the above code to your main JavaScript file, save and then run the app using the command node [my_file_name].js. Then you should be able to navigate to http://localhost:3000/ and see 'Hello World'.

Note: If you are unfamiliar with arrow functions, I recommend having a quick read of this blog post going over some JavaScript techniques new to ECMAScript 6.

Adding a Router

We can separate our programmatic and human web, by adding a suffix to all our API (programmatic) paths. We do this by using a router, which is included in the Express framework.

const express = require('express');

const app = express();

const router = express.Router();

const port = 3000;

// url: http://localhost:3000/

app.get('/', (request, response) => response.send('Hello World'));

// all routes prefixed with /api

app.use('/api', router);

// using router.get() to prefix our path

// url: http://localhost:3000/api/

router.get('/', (request, response) => {

  response.json({message: 'Hello, welcome to my server'});

});

// set the server to listen on port 3000

app.listen(port, () => console.log(`Listening on port ${port}`));

Running the above code and navigating to http://localhost:3000/api/ will show you your json message: {message: 'Hello, welcome to my server'}.

Using URL parameters

Now that we've got our server setup and isolated our API layer using a router, we can start using some URL parameters to do things!

Sending HTTP requests

I recommend using Postman to test APIs, because it's a lovely little GUI for building HTTP requests, you can save them and collect a number of different requests and save them as a suite. You can then even set up expected results for each of the requests, allowing you to unit test your API!

// all of the code from the previous section should be here

const url = require('url');

router.get('/stuff', (request, response) => {

  var urlParts = url.parse(request.url, true);

  var parameters = urlParts.query;

  var myParam = parameters.myParam;

  // e.g. myVenues = 12;

  var myResponse = `I multiplied the number you gave me (${myParam}) by 5 and got: ${myParam * 5}`;

  response.json({message: myResponse});

});

In the above example, using my example value you should receive a json response equal to: {"message":"I multiplied the number you gave me (20) by 5 and got: 100"}.

Note: For those not using Postman or otherwise sending a HTTP request, you can test this route using the following URL: http://localhost:3000/api/stuff?myParam=12.

CORS

If you're looking to use a HTTP server in production then you will know that we have to take CORS (Cross-Origin Resource Sharing) into account to allow given origins to access our server.

// all our previous code should be here

// this array is used for identification of allowed origins in CORS

const originWhitelist = ['http://localhost:3000', 'https://example.net'];

// middleware route that all requests pass through

router.use((request, response, next) => {

  console.log('Server info: Request received');

  let origin = request.headers.origin;

  // only allow requests from origins that we trust

  if (originWhitelist.indexOf(origin) > -1) {

    response.setHeader('Access-Control-Allow-Origin', origin);

  }

  // only allow get requests, separate methods by comma e.g. 'GET, POST'

  response.setHeader('Access-Control-Allow-Methods', 'GET');

  response.setHeader('Access-Control-Allow-Headers', 'X-Requested-With,content-type');

  response.setHeader('Access-Control-Allow-Credentials', true);

  // push through to the proper route

  next();

});

The above code implements a middleware route that all requests sent to the /api namespace will be routed through before continuing to their destination route. This is ideal for adding CORS headers to requests from our whitelist of origins.

source: blog.leonhassan.co.uk