But first..

..a quick JavaScript refresher

let / const

const a = 5

a = 6 // nope!!  "TypeError: Assignment to constant variable."

let b = "hey"

b = "yeh"

{
  const c = a + b
  console.log({ c }) // prints { c: "5yeh" }
}

console.log({ c }) // "ReferenceError: c is not defined"

// (JS can't make up it's mind about periods in Error messages)

arrow functions

function traditionalFunction(a, b) {
  // `this` and `arguments` implicitly defined
}

const arrowFunction = (a, b) => {
  // nothing special here.. just variables from surrounding closures
}

const implicitReturn = () =>
  "without curlies, arrow functions implicitly return their expression"

const add = a => b => a + b

add(1)(7) // 8

const add3 = add(3)

add3(5) // 8

const subtract = a => b => a - b

classes

class Point {
  constructor(x, y) {
    this.x = x
    this.y = y
  }

  distance(point) {
    const a = this.x - point.x
    const b = this.y - point.y
    return Math.sqrt(omg don't use classes to store data)
  }

  static clone(point) {
    return new Point(point.x, point.y);
  }
}

whew.. that's better

const p1 = { x: 5, y: 7 }
const p2 = { x: -1, y: 2 }

const distance = (left, right) => {
  const a = left.x - right.x
  const b = left.y - right.y
  return Math.sqrt(a ** 2 + b ** 2)
}

const clonedPoint = { ...p2 }

rest / spread

const p1 = [ 1, 2, 3, 4 ]
const p2 = [ ...p1 ]

const sum = (...numbers) => numbers.reduce((t, n) => t + n, 0)
sum(1, 3) // 4
sum(5, 5, 2, 7) // 19

const [ head, ...tail ] = p2

const user = { name: "someone", email: "someone@email.com" }

const { email, ...otherUserInfo } = user

const PracticalComponent = ({ name = "unknown", ...otherProps }) =>
  <div>
    <h1>Hello, {name}</h1>
    <UserProfile user={otherProps} />
  </div>

template strings

const greet = name => `Hello, ${name || "what's your name?"}`

const literallyAnything = gql`
  query {
    users {
      favoriteES2015Feature
    }
  }
`

Promises

const a = Promise.resolve(5)

const b = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve(10)
  }, 5000)
})

const userObjP = fetch("/user").then(res => res.json())

userObjP
  .then(user => console.log("current user: ", user))
  .catch(err => console.error("failed to fetch user: ", err))

async / await

const logUser = async () => {
  try {
    const res = await fetch("/user")
    const user = await res.json()
    console.log("current user: ", user)
  } catch (err) {
    console.error("failed to fetch user: ", err)
  }
}

modules

import App from "./components/app"
import { log, randomFn } from "./utils"

export const abc = () => "abc"

export default (props) => <App {...props} />

but wait, there's more...........

• Enhanced Object Literals
• Set, Map
• WeakSet, WeakMap
• Generator functions
• Unicode
• Proxies
• Symbols
• Additions to the Math, Number, String, and Object APIs
• Binary/Octal literals
• Reflect API
• Tail calls

but wait, there's EVEN MORE

• ES2016
• ES2017
• ES2018
• ...

feel refreshed?

npm

npm

npm init # in a new directory

npm install --save micro

npm test

npm start

npm run other-scripts

package.json

{
  "name": "example-project",
  "version": "1.0.0",
  "description": "",
  "main": "src/index.js",
  "dependencies": {
    "micro": "^8.0.3"
  },
  "scripts": {
    "start": "node .",
    "test": "echo 'Write some tests!'"
  }
}

Node.js

(again)

What is it?

• Written by Ryan Dahl in 2009
  • https://www.youtube.com/watch?v=jo_B4LTHi3I
• JavaScript on a server
• JavaScript in a desktop app
• JavaScript in a command line app

But what is it?

• libuv
• V8
• Standard Library

The Event Loop

nodejs.org/dist/latest-v8.x/docs/api/