express.js.md

Express js

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Express js installation

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Express Installing:

Assuming you’ve already installed Node.js, create a directory to hold your application, and make that your working directory.

mkdir myapp
cd myapp
npm init

entry point: (index.js)


npm install express

To install Express temporarily and not add it to the dependencies list:

npm install express --no-save

index.js

  const express = require('express')
  const app = express()
  const port = 3000

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

  app.listen(port, () => {
    console.log(`Example app listening on port ${port}`)
  })

Running Locally

 index.js  or  app.js  or  server.js

Express application generator:

 npx express-generator
 npm install -g express-generator
 express
 express -h

Usage: express [options] [dir]

 express --view=pug myapp

Then install dependencies:

    cd myapp
    npm install

On MacOS or Linux, run the app with this command:

DEBUG=myapp:* npm start

On Windows Command Prompt, use this command:

set DEBUG=myapp:* & npm start

On Windows PowerShell, use this command:

PS> $env:DEBUG='myapp:*';

    npm start
            
OR
    
    DEBUG=backend:* npm start

Then load http://localhost:3000/ in your browser to access the app.

The generated app has the following directory structure:

    .
    ├── app.js
    ├── bin
    │   └── www
    ├── package.json
    ├── public
    │   ├── images
    │   ├── javascripts
    │   └── stylesheets
    │       └── style.css
    ├── routes
    │   ├── index.js
    │   └── users.js
    └── views
        ├── error.pug
        ├── index.pug
        └── layout.pug