Host a Node.js API on Heroku

Sometimes there is a need to set up a Node.js API to test out an idea. Heroku offers the possibility of doing so but by default, it assumes that there’s a web process in the deployment. Here’s how to work around that so that this can happen:

(Wanna get straight to the code? https://github.com/YFLooi/task-list-app-backend)

First, let’s set up an Express backend. Install the following packages:

yarn add express cors dotenv
yarn add --dev cross-env

cross-env enables using bash-style env variables in the package.json start script.

Set up a repo (e.g. “npm init”). In package.json, include the following lines:

{
  ...
  "main": "server.js",
  ...
 "engines": {
   "npm": "6.4.1",
   "node": "14.15.3"
 },
  ...
 "scripts": {
    "start": "cross-env PORT=$PORT node server.js"
    "heroku-postbuild": "npm install",
    "test": "echo \"Error: no test specified\" && exit 1"  
  },
  ...
}

Notice the “start” script? “$PORT” is attached by Heroku’s HTTP routing stack when the deployed app loads (ref in Heroku docs). This ensures calls to “https://appName.herokuapp.com/” can be received by the Nodejs API.

To ensure this “start” script runs on load, declare the following Procfile at the root of the repo:

web: node server.js

The weird name is because Heroku expects a “web” process, hence the Nodejs API has to be declared this way.

Now to set up server.js in the root of the repo. Let’s do a simpler version of the one in the example Github repo that returns some JSON:

const express = require(“express”);
const server = express();
const port = process.env.PORT || 3500;
const cors = require("cors");
require("dotenv").config();
server.use(cors());
server.get(`/`, async (req, res) => {
  console.log(`Call made to root route at “/”. Returning json`);
  res.json({"message":"You have contacted your Nodejs API on Heroku!"});
});
server.listen(port, () => {
  console.log(`Server is listening on http://localhost:${port}`);
});

Time to deploy. I’ m going to refer to the Heroku CLI in this example (download here).

Head to your Heroku account to create a new app. Copy the Heroku Git url to your app, you’ll find it here under the app’s “Settings”:

Add this Git url to the repo’s Git remote:

git remote add heroku https://git.heroku.com/your-heroku-app.git

Log into your Heroku account from the command line using “heroku login”. You’ll be redirected to a browser to insert your credentials.

Now that you are logged in, deploy by running the following:

git push heroku master

Once the process is complete, spin up the web process with:

heroku ps:scale web=1

Go to your Heroku account dashboard. Click on “Open App” then copy the resulting url in your browser. It looks something like “https://your-heroku-app.herokuapp.com/”

Now to check if your Node.js API is up and running. Using Postman, set up a a GET request. Here’s as an example:

Click “Send”. If all is well, the response would return:

{"message":"You have contacted your Nodejs API on Heroku!"}