Intro to nodeJS

Intro to NodeJS

• Node is a version of Javascript that works outside the browser. It can run on the command line and on servers
• Node is used for writing backend applications without a browser, though it can be used to manage the server in addition to the software you write for a browser
• Download Node

NPM

• NPM is the Node Package Manager
• A package manager is a kind of app store for the command line, sometimes for a particular operating system, such as Homebrew for Mac, or for a specific programming language.
• NPM is the package manager for Node software
• Each node program you write that will also use NPM software needs a package.json file to list the NPM packages you want to include and use

Running Your Node.js App Locally

Set Up Your Files

Create a folder called my-app and put your files in it like this:

my-app/
  server.js
  public/
    index.html
    main.js
    main.css

The public/ folder holds everything the browser sees. server.js sits outside it.

Run the Server!

Open your terminal, navigate to your project folder, and start the server:

cd my-app
node server.js

You should see:

Server running at http://localhost:3000

Open your browser and go to http://localhost:3000.

To stop the server, press Ctrl+C in the terminal.

Express

• Express is a node package
• It is a simple web framework for node that can host files and get user input

What does Express do for us? Why are we using it?

Let’s visit the website for Express.

It explains that Express is a fast, unopionated minimalist web framework. Fast is obvious. Unopinionated is coder-speak for: “you can write code any which way you please. There isn’t a single way you have to write it if you use our library with it.” Okay, but what is a web framework?

Express provides a simple way (a mini “language”) to serve pages. It is like a switchboard operator that receives a call (“Hello, I’d like to speak to lee in Henley-4562”). What are we routing? When a user requests a particular webpage, that gets routed via our code, and specific content (“a view”) is served.

How does this work? Express looks for the route specified in the URL bar.

MyWebsite.com/theRouteIamRequesting

the Route looks like a sub-folder, but it’s actually a bit of information that is communicated. Express takes this info, and then figures out what to display.

var express = require(‘express’);

//you can now create an ‘app’ //This app holds an instance of express and can use its functionality

var app = express();

var server = app.listen(4000); //listens on port 4000. Triggers callback.

app.use(express.static(‘public’)); ```

This means http://localhost:4000 will host the project

## Running Your Node.js App Locally with Express

### Step 1 — Set Up Your Files

Create a folder called `my-app` and put your files in it like this:

my-app/ server.js public/ index.html main.js main.css

The `public/` folder holds everything the browser sees. `server.js` sits outside it.

---

## Step 2 — Install Express

Open your terminal, navigate to your project folder, and run:

```bash
cd my-app
npm init -y
npm install express

npm init -y creates a package.json file for your project. npm install express downloads Express into a node_modules/ folder.

Step 3 — Run the Server

node server.js

You should see:

Server running at http://localhost:3000

Open your browser and go to http://localhost:3000.

To stop the server, press Ctrl+C in the terminal.