Coding the application

Now that the git repository and the node module structure are setup, we are ready to start coding the application.

This application will be a simple hello world.

Instaling our dependencies

In node.js, the dependencies are listed in the package.json file. All dependencies from this file can be installed using the command npm install ..

An other dependency can be installed and added to the package.json using: npm install name@version --save.

Our application will depend on: express@4.3.1.

So install it using:

$ npm install express@4.3.1 --save

Hello World

Express is web application framework for node, it makes it really easy to write web application using node.

Write in a file named main.js:

var express = require("express");
var app = express();

app.get('/', function(req, res) {
  res.send('Hello World!');
});

var port = Number(process.env.PORT || 5000);
app.listen(port, function() {
  console.log("Listening on " + port);
});

This code will simply create an application using Express. Define an handling method for a get request on the root path. And start the web server on the port defined by the environment variable PORT or 5000.

Run Script

Heroku convention needs a Procfile file that defines how to start the application. You can learn more about Procfile in the Heroku documentation.

Write in a file named Procfile:

web: node main.js

This file simply tell Heroku that for starting this application, it needs to start a web dyno by running the command node main.js.