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CoffeeScript vs. ECMAScript 6
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Florian Plank
February 26, 2015
Programming
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CoffeeScript vs. ECMAScript 6
Florian Plank
February 26, 2015
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Transcript
Ruby ECMAScript 6 vs.
CoffeeScript ECMAScript 6 vs.
None
flickr.com/photos/mcgovernville
Disclaimer
CoffeeScript
Transpilers
The elevator pitch
“ Expose the good parts of JavaScript in a simple
way.
“ It’s just JavaScript.
Readable Natural language Speed Backward compatible Sturdy
Whitespace sensitive
user = name: "John" age: 23
No semicolons* No round brackets** No curly braces*** No “var”
user = name: "foo" ! if user.name is "bar" console.log
JSON.stringify user
Lexical scope and variable safety
name = "John" age = 23 ! ! (function() {
var age, name; name = "John"; age = 23; ! }).call(this);
<Opinion />
EcmaScript 6
ES6 also known as —
Harmony also known as —
ES.next also known as —
ES 2015 also known as —
JavaScript 2015 also known as —
JS 9000 also known as —
What’s in a name?
Mocha ! LiveScript ! JavaScript ! ! ! ! JScript
! ! ! ! ! ECMA–262 —The standard ECMAScript —The
language
“ ECMAScript was always an unwanted trade name that sounds
like a skin disease. ! — Brendan Eich
ES 1 ES 2 ES 3 ES 4 ES 5
ES 5.1 ES 6 ES 7 1997 1998 1999 — Abandoned 2009 2011 2015 — TBA
TC39
JavaScript 1.1 ECMAScript 1 JavaScript 1.5 ECMAScript 3 JavaScript 2.0
ECMAScript 6 (Harmony)
JavaScript™
Can I use it?
None
None
None
None
None
None
CoffeeScript vs. ECMAScript 6
JavaScript (ECMAScript 5)
JavaScript (ECMAScript 5) JavaScript (ECMAScript 6)
JavaScript (ECMAScript 5) JavaScript (ECMAScript 6) CoffeeScript
JavaScript (ECMAScript 5) JavaScript (ECMAScript 6) CoffeeScript
JavaScript (ECMAScript 5) JavaScript (ECMAScript 6) CoffeeScript And here’s why…
None
What’s common?
Classes
class Person extends Actor constructor: (@firstName, @lastName) -> fullName: ->
"#{@firstName} #{@lastName}"
class Person extends Actor { ! constructor(firstName, lastName) { this.firstName
= fistName; this.lastName = lastName; } fullname() { return `${this.firstName} ${this.lastName}`; } ! }
class Person extends Actor { get name() { // return
... } set name(value) { // ... } }
(Fat) arrow functions
Account = (customer, cart) -> @customer = customer @cart =
cart ! $('.cart').bind 'click', (event) => @customer.purchase @cart
function Account(customer, cart) { this.customer = customer; this.cart = cart;
$('.cart').bind('click', (e) => { this.customer.purchase(this.cart); }); }
Default function parameters
fill = (liquid = "coffee") -> # ...
function fill(liquid = "coffee") { // ... }
Destructured assignment
[name, age] = ["John", 23] ! response = name: "John"
email: "
[email protected]
" age: 23 ! {name, age} = response
var options = { repeat: true, save: false }; !
var { repeat, save } = options;
var options = { repeat: true, save: false, rules: {
custom: 10, } }; ! var { repeat, save, rules: { custom }} = options;
Rest and spread operators
String interpolation
What’s extra?
JavaScript (ECMAScript 5) JavaScript (ECMAScript 6) CoffeeScript
Block–scoped variables
var es = []; ! for (var i = 0;
i < 10; i++) { let c = i; es[i] = function () { console.log("ES" + c); }; } ! es[6](); // => ES6
const FOO = "bar"; ! console.log(FOO); // => "bar" !
FOO = "foo"; ! console.log(FOO); // => "bar" ! const FOO = "baz"; ! console.log(FOO); // => "bar"
Generators*
function* idMaker(){ var index = 0; while(true) yield index++; }
! var gen = idMaker(); ! console.log(gen.next().value); // 0 console.log(gen.next().value); // 1 console.log(gen.next().value); // 2
Modules
// file A: export const sqrt = Math.sqrt; export function
square(x) { return x * x; } export function diag(x, y) { return sqrt(square(x) + square(y)); } ! // file B: import { square, diag } from 'lib'; console.log(square(11)); ! // file C: import * as lib from ‘lib'; console.log(lib.square(11));
Promises
function timeout(duration = 0) { return new Promise((resolve, reject) =>
{ setTimeout(resolve, duration); }); } ! var p = timeout(1000).then(() => { return timeout(2000); }).then(() => { throw new Error("hmm"); }).catch(err => { return Promise.all([timeout(100), timeout(200)]); });
Sets and Maps
var s = new Set(); s.add(“a").add("b").add("a"); ! s.size === 2;
s.has("a") === true;
var m = new Map(); m.set("hello", 42); ! m.set(s, 34);
m.get(s) == 34;
Symbols
var firstName = Symbol(); var person = {}; ! person[firstName]
= "Nicholas"; console.log(person[firstName]);
var firstName = Symbol(); var person = {}; ! person[firstName]
= "Nicholas"; console.log(person[firstName]);
const MY_KEY = Symbol(); let obj = {}; ! obj[MY_KEY]
= 123; console.log(obj[MY_KEY]);
const MY_KEY = Symbol(); ! let obj = { [MY_KEY]:
123 };
const FOO = Symbol(); ! let obj = { [FOO]()
{ return 'bar'; } }; ! console.log(obj[FOO]());
Iterables & for … of loops
let values = [1, 2, 3]; ! for (let i
of values) { console.log(i); }
What’s missing?
JavaScript (ECMAScript 5) JavaScript (ECMAScript 6) CoffeeScript
List comprehension
say(letter) for letter in ['A', 'B']
johns = (n for n in ['John', 'Marcy'] when n
is 'John')
users = john: 23, marcy: 29 ! ageReport = for
name, age of users "#{name} is #{age}"
Whitespace sensitive
“Everything’s an expression” Implicit return
foo =-> "bar"
grade = (student) -> if student.excellentWork "A+" else if student.okayStuff
if student.triedHard then "B" else "B-" else "C" eldest = if 24 > 21 then "Liz" else "Ike"
[lastName, age] = if name == 'John' then ['Doe', 23]
else if name == 'Marcy' then ['Murcy', 29] else ['Unknown' ] ! console.log lastName, age
Postfix conditionals
console.log("42") if question is true
Operators and aliases
invite(user) if user? # typeof user !== "undefined" && user
!== null ! ! name = userName ? 'John'
launch() if ignition is on ! volume = 10 if
band isnt SpinalTap ! letTheWildRumpusBegin() unless answer is no ! letIn() if name in ['John', 'Marcy']
Ranges
countdown = (num for num in [10..1])
Verdict?
Try it now, switch later (where applicable)
“ But one thing is for certain: we must embrace
the moving target.
http://coffeescript.org/ https://kangax.github.io/compat-table/es6/ https://speakerdeck.com/polarblau/an-evening-with-coffeescript https://github.com/lukehoban/es6features https://leanpub.com/understandinges6/read http://www.wintellect.com/devcenter/nstieglitz/5-great-features- in-es6-harmony http://rauchg.com/2015/ecmascript-6/ http://code.tutsplus.com/articles/use-ecmascript-6-today-- net-31582
http://blog.500tech.com/on-coffeescript-and-es6/ https://github.com/ericdouglas/ES6-Learning
JOIN US!
THANKS! @polarblau