02express_setup.md

Express Setup

Create a folder called backend and create server.js in it. Also do npm init -y to intialize npm and then do npm install express

Also modify package.json:

{
  "name": "backend",
  "version": "1.0.0",
  "description": "",
  "main": "server.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "node server.js",
    "dev": "nodemon server"  // add this line
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "express": "^4.18.2"
  }
}

Now we can run npm run dev to run our application

Set up express in the standard way:

const express = require('express');

const app = express();

// listen for requests
app.listen(4000, ()=>{
    console.log('Listening on port 4000');
})

// Routes
app.get('/', (req,res)=>{
    res.json({msg: 'Welcome to the app'});
});

Now create a .env file in the backend folder - this stores all environment variables

PORT=4000

The idea is if you're pushing this to github, you make put this in the gitignore so that everything here stays private

To actually use this, do

npm install dotenv

This loads the variables from the .env file into the process.env object - available globally in a nodejs environment

Now you can update server.js as follows:

require('dotenv').config()

const express = require('express');

const app = express();


// Listen at port 4000
app.listen(process.env.PORT, ()=>{
    console.log('Listening on port 4000');
})


// Routes
app.get('/', (req,res)=>{
    res.json({msg: 'Welcome to the app'});
});

Can also add some middleware:

//...
app.use((req,res,next)=>{
    console.log('Path:',req.path,'  Method:' ,req.method);
    next();
});