Node

Node

Node takes the JS complier in chrome browser and adds some server logic and io stuff so you can use it on the backend. So node filename lets you run arbitrary js logic where console.log is std.out

JS is a language

Assert

var assert = require('assert');
assert(5 > 7);

Versions

• Even numbered releases are LongTerm Support(LTS); they generally receive 30 months of support once they become LTS. Given codename

  • V20 is iron and ends support in April 2026

  • V18 is hydrogen and ends support in April 2025

• Odd numbered releases are current releases and are supported for six months.

Express(4.16)

Most Basic Code

const express = require('express')

const app = express()

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

app.listen(8000, function () {
  console.log('Example app listening on port 8000!')
})

Can run with node [filename]

Overview

Middleware have access to request object (req), response object (res), and the next middleware ft(next). If you don't respond with res, call next()

Run for every request

app.use(function (req, res, next) {
  console.log('Request Type:', req.method)
  next()
})

Run for specific urls

app.get('/users/:userId/books/:bookId', function (req, res) {
  res.send(req.params) 
  // => { "userId": "34", "bookId": "8989" }
})

Types

• app.use(...) => for any HTTP request

• app.get(...) => for get request

Globals

• __dirname => full from root name of the directory that the executing script resides from

• process.env => environment at start of runtime can use to access PATH and other env variables like process.env.NODE_ENV

export NODE_ENV=production while running to run in production mode, many libs check for it including express which will not print out stack traces and config