Simple API Server

This chapter explains how to create a simple Node.js API server using the Express.js framework.

First, install the dependencies.

$ npm install --save [email protected]

Router

Create a new file ./src/router/index.js and define a router.

const express = require('express');
const usersRoutes = require('./users');

exports.createRouter = function () {
  const router = express.Router({
    mergeParams: true
  });

  router.get('/users', usersRoutes.index);
  router.get('/users/:id', usersRoutes.show);

  return router;
};

Routes

Create a new routes file ./src/router/users.js which will expose user-related actions.

exports.index = function (req, res) {
  res.send('list of users');
};

exports.show = function (req, res) {
  let id = req.params.id;
  res.send(`user with ID${id}`);
};

Server

Open the ./src/index.js file and paste the content below.

const express = require('express');
const {createRouter} = require('./router');

exports.Server = class {

  constructor(config) {
    this._config = config;
    this._app = null;
    this._server = null;
  }

  listen() {
    return new Promise((resolve) => {
      if (this._server) return this;

      this._app = express();
      this._app.use('/', createRouter());

      let {port, host} = this._config;
      this._server = this._app.listen(port, host, resolve);
    });
  }

  close() {
    return new Promise((resolve) => {
      if (!this._server) return this;

      this._server.close(resolve);

      this._server = null;
      this._app = null;
    });
  }

}

Configuration

Open the ./package.json file and set configuration variables and a start script.

{
  "config": {
    "server": {
      "port": 4444,
      "host": "127.0.0.1"
    }
  },
  "scripts": {
    "start": "node ./src/scripts/start.js"
  }
}

Create a new configuration file ./src/config.js and set application variables.

exports.serverConfig = {
  port: process.env.npm_package_config_server_port,
  host: process.env.npm_package_config_server_host
};

Create a startup script ./src/scripts/start.js which start the application.

const {Server} = require('..');
const {serverConfig} = require('../config');

const app = new Server(serverConfig);
app.listen().then(() => {
  console.log('Server started');
}).catch((error) => {
  app.close();
  console.log('Error', error);
});

Run the npm start command to start the server then navigate to http://localhost:4444/users to see the result. Use npm config command to configure the server.