9.3 Using Node.js

New Material

Running Node (potentially on your own computer) lets you build and test a full stack application easily before pushing your files to a server.

Prerequisites

We recommend you complete 1.2 Command Line to prepare for this tutorial.

Install Node

This tutorial covers a basic install process for Node.js. You will run these in your Terminal program.

Caution

If you are developing on your own machine, please complete 1.3 Git and Gitub Desktop. Node is already installed on Github Codespaces.

Mac

1. Install Homebrew (Mac package manager) using their instructions
2. Install Node using Homebrew

brew install node

Windows

Windows Users

Many Unix commands do not work in Windows PowerShell. Install and use Git Bash instead.

1. Install Scoop (Windows package manager) using their instructions
2. Install Node using Scoop

scoop bucket add main
scoop install main/nodejs-lts

3. Confirm installation

node -v
# -> v24.7.0
npm -v
# -> 11.5.1

Open Node interactive shell

Test Javascript in Node’s interactive shell.

1. Type node on the command line and press return to open the interactive shell.
2. At the > prompt, type 1+1 and press return. Node will evaluate your expression and return the result.

> 1+1
2

3. Node is just Javascript, so almost any code will run.
4. Cancel any process in the Terminal using Ctl+c

Run a script with Node

Codespaces

Inside an empty Codespaces project…

1. Create a file named index.js and paste the below code.

let greeting = "Hello, from Node";
console.log(greeting);

2. In the Terminal, run the script with:

node index.js

Your Own Machine

1. Create a new folder named: cron-demo and open it in VS Code (in Mac you can just drag the folder from the finder to the VS Code icon in the dock)
2. Create a file in this folder named index.js and paste the below code.

let greeting = "Hello, from Node";
console.log(greeting);

3. In the Terminal, run the script with:

node index.js

Note

1. The name index.js is arbitrary. Other names like server.js and app.js are also popular for different use cases.
2. Notice that Node stops automatically after it runs all the code.

Initialize a new project with NPM

Every Node.js project has a package.json to store project dependencies and other metadata.

Codespaces

Inside an empty Codespaces project…

Your Own Machine

Inside the cron-demo in VS Code (created above)

1. Open the Terminal in your editor.
2. Run npm init to initialize a new project. Press return at each prompt. This creates a package.json file with data you entered.
3. Open your new package.json file. Confirm the main field is set to index.js.
4. Add a new sub-property under scripts. Add a comma after the test property, then add "start": "node index.js" below it (see outcome below).
5. Run npm run start which runs the command stored in start.

Outcome

{
  "name": "cron-demo",
  "version": "1.0.0",
  "description": "",
  "license": "ISC",
  "author": "",
  "type": "commonjs",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "node index.js"
  }
}

Package Managers

There are several Node package managers, but NPM is a popular choice.

Install Nodemon using NPM

Nodemon is an NPM package that automatically restarts your node application when it detects file changes in your the project directory.

1. Install the nodemon package globally npm install -g nodemon (the -g flag makes it global)
2. Run index.js using nodemon (instead of node) nodemon index.js
3. Edit and save index.js. Nodemon will restart your script each time you save.

[nodemon] restarting due to changes...
[nodemon] starting `node index.js`

4. Exit the process with Ctl+C (this exits any process on the Terminal).

---

Use the Cron package

Cron is an NPM package that executes scripts on a schedule (e.g. each/second, once/day) or at particular times. Use it to automate any common task like database backups, etc..

1. Run npm i cron --save in the Terminal (i is a shortcut for install, --save adds a dependency to your project’s package.json)
2. In package.json a new dependency has been added, as well as a new node_modules folder, where the cron package and packages it uses was just installed.
3. Add the code below to your index.js file.

// require the package
var CronJob = require('cron').CronJob;
// create a new instance
var job = new CronJob(
  '* * * * * *',
  function() {
    console.log('The local time is: '+ new Date().toLocaleString());
  },
  null, true, 'America/New_York'
);

4. Run it with nodemon index.js in the Terminal.
5. Use crontab.guru to experiment with the time.