Node.js

install & update in ubuntu

ubuntu default install is low-version:

sudo apt install nodejs npm

Update to stable:

sudo npm install -g n
sudo n stable
sudo npm install -g npm

need to restart shell to use new version!

node

Node.js is a JavaScript run-time environment.

It allows developers to write JavaScript outside of a browser.

Difference
Node.js	no DOM	require
Browser	DOM	import

(DOM = Document Object Model)

• CMD

  node app.js
  node app.js 1 2 3
  

  // retrieve arguments
  process.argv.forEach((val, index) => {console.log(`${index}: ${val}`)})
  

• REPL

  node
  

  Special Commands:

  • .help
  • .clear
  • .load <file>
  • .save <file>
  • .exit the REPL.

• Core Module: process

  process.exit()
  process.env.ENV_VAR
  

• Input from CMD

  const readline = require('readline').createInterface({
    input: process.stdin,
    output: process.stdout
  })
  
  readline.question(`What's your name?`, 
    name => {
      console.log(`Hi ${name}!`);
      readline.close();
    }
  )
  

• Expose

  // car.js
  const car = {}
  module.exports = car
  // in other files:
  const car = require('./car.js')
  

  // car.js
  exports.car = {}
  // in other files:
  const items = require('./car.js')
  items.car
  

npm: Node Package Manager

npm install # based on package.json, install in local node_modules folder.
npm install <pkg> # specific, install in local folder, and add it to package.json.
npm install <pkg>@version # install old versions

npm install -g <pkg> # install in global folder.
npm install -S <pkg> # --save, also add ref in package.json
npm install -D <pkg> # --save-dev, also add dev-dependencies in package.json
npm root -g # the global folder. (/usr/local/lib/node_modules)

npm uninstall <pkg> 
npm uninstall -S <pkg>  # --save, also remove ref in package.json
npm uninstall -D <pkg>  # --save-dev, also remove dev-dependencies in package.json
npm uninstall -g <pkg>  # global

# check package installed versions
npm list # list all installed packages with version. (recursive! maybe very long)
npm list --depth 0 # use this instead.

# check package installed/wanted/latest versions
npm outdated

# update packages only to the wanted version!!! 
npm update # all
npm update <pkg> # a specific

# update to the latest versions
npm install <pkg>@latest

# force update all package to latest versions
npx npm-check-updates -u 
npm install

init a project

npm init -y # --yes

this will create a package.json.

// package.json
{
  "name": "nerf",
  "version": "1.0.0",
  "description": "",
  "main": "source.js",
  "dependencies": {
    "three": "^0.129.0"
  },
  "devDependencies": {},
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC"
}

React provides a better init setup by:

npx create-react-app <name>

It installs lots of default packages.

npx: Node Package Runner

npm install cowsay # executables in .bin
# how to run
./node_modules/.bin/cowsay
# a better solution
npx cowsay

npx node@10 # run specific version of node
npx https://xxx # run code from web

package.json

{
  "name": "test-project",
  "version": "1.0.0",
  "description": "A Vue.js project",
  "main": "src/main.js",
  "private": true,
  "scripts": {
    "dev": "webpack-dev-server --inline --progress --config build/webpack.dev.conf.js",
    "start": "npm run dev",
    "unit": "jest --config test/unit/jest.conf.js --coverage",
    "test": "npm run unit",
    "lint": "eslint --ext .js,.vue src test/unit",
    "build": "node build/build.js"
  },
  // Production
  "dependencies": {
    "vue": "^2.5.2"
  },
  // Development
  "devDependencies": {
    "autoprefixer": "^7.1.2",
    "babel-core": "^6.22.1",
  },
  "engines": {
    "node": ">= 6.0.0",
    "npm": ">= 3.0.0"
  },
  "browserslist": ["> 1%", "last 2 versions", "not ie <= 8"]
}

package-lock.json: the exact environment to reproduce the code.