Express: Hello World!

README.md

Express: Hello World!

Prerequisites

1. Initialized npm project with package.json file. See: Getting started with npm.
2. express installed as project dependency.
3. Entry page (i.e. server.js) present in the project root.

Example directory structure

project-root
    ├── node_modules
    ├── package-lock.json
    ├── package.json
    └── server.js

Instructions

1. Load project dependencies:

   const express = require('express');

2. Create an express server. The interface for every module is unique. Express wants you to start by invoking the function that express exports to require().

   const app = express();

   • express() returns an object. It includes many methods that come in handy; today's favourite is app.get() which allows us to attach middleware to GET requests.

3. Add endpoint handler for GET / requests (i.e. the home page):

   app.get('/', (request, response) => {
     response.send('Hello World!')
   })

4. Set a port the server will listed to. process.env.PORT points to an optional .env file (see dotenv) that will default to 3000 if it doesn't exist.

   const PORT = process.env.PORT || 3000;

5. Start the server.

   app.listen(PORT, function(){
     console.log(`Listening on port ${PORT}`);
   });

   • The server will start inside the terminal window (making it pretty useless, besides logging to the console).

Related Gists

• [Express: Add an additional GET endpoint handler]
• Express: Catch 404 Not Found errors
• Express: Serving static files

package.json

{
  "name": "hello-express",
  "version": "1.0.0",
  "description": "An introductory express app",
  "main": "server.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "Tony Grimes",
  "license": "MIT",
  "dependencies": {
    "express": "^4.17.1"
  }
}

server.js

const express = require('express');
const app = express();

app.get('/', (request, response) => {
  response.send("Hello World!");
})

const PORT = process.env.PORT || 3000;

app.listen(PORT, function() {
  console.log(`Example app listening at http://localhost:${PORT}`);
})