CoffeeScript

Script
by
Scott Leberknight

Created by Jeremy Ashkenas

https://github.com/jashkenas/coffee-script

Compiles to JavaScript

var cube, cubes, num;
cube = function(x) {
return Math.pow(x, 3);
};
cubes = (function() {
var _i, _len, _ref, _results;
_ref = [1, 2, 3, 4, 5];
_results = [];
for (_i = 0, _len = _ref.length; _i < _len; _i++) {
num = _ref[_i];
_results.push(cube(num));
}
return _results;
})();
console.log(cubes);

JavaScript

cube = (x) -> x * x * x
cubes = (cube num for num in [1, 2, 3, 4, 5])
console.log cubes

OS X
Install Homebrew

brew install node

curl http://npmjs.org/install.sh | sh

npm install coffee-script

coffee -v

http://mxcl.github.com/homebrew/

Linux*
install node and npm
(http://joyeur.com/2010/12/10/installing-node-and-npm/ )

npm install coffee-script

coffee -v

(* Windoze people can uze these instructions on Cygwin)

$ coffee -c my.coffee
$ node my.js
[ 2048, 4096, 6144, 8192, 10240 ]

$ coffee
coffee> nums = (x * 1024 for x in [2..10] by 2)
2048,4096,6144,8192,10240

coffee> typeof(nums)
object

coffee> nums.length
5

coffee> nums[4]
10240

coffee> quit()

$ coffee --watch my.coffee
[ 2048, 4096, 6144, 8192, 10240 ]
[ 1024, 2048, 3072, 4096, 5120 ]

Everything's an expression
result = if (2 > 1) then "Yep" else "Hmmmm..."
console.log result
=> Yep

book = "I Am America (And So Can You!)"

var book;
book = "I Am America (And So Can You!)";

JavaScript

http://www.amazon.com/Am-America-So-Can-You/dp/0446580503

Significant Whitespace

if isFood(animal)
strangle()
eat()
else
slitherAlong()22

Significant Whitespace

if isFood(animal)
strangle()
eat()
else
slitherAlong() 23

noop = ->

-> 'The answer is 42'

console.log do -> 'What is the question?'

answerer -> 'The answer is 42'

mult = (x, y) -> x * y

mult = (x, y) -> x * y

var mult;
mult = function(x, y) {
JavaScript
return x * y;
};

console.log do -> 'What is the question?'

console.log((function() {
return 'What is the question?';
})());

JavaScript

a = [1, 2, 3, 4, 5]

a[1..2] # inclusive range: [2, 3]
a[1...2] # exclusive range: [2]
a[0..-1] # [1, 2, 3, 4, 5]
a[2..-2] # [3, 4]

range = [1..10]
range = [1..21]
range = [1..22] # Inflection pt! (*)
range = [1..100]
range = [1..100000]

(* in version 1.0.1 )

fellowship =
wizard: 'Gandalf'
hobbits: ['Frodo', 'Pippin', 'Sam']

delta = 'u0394'
greekUnicode = { delta }

var delta, greekUnicode;
delta = 'u0394';
greekUnicode = {
JavaScript
delta: delta
};

CoffeeScript JavaScript
==, is ===
!=, isnt !===
and &&
or ||
of in
in (no equivalent)
@, this this
true, yes, on true
false, no, off false

goodStudent = yes if grade in ['A', 'B']

stop() unless greenLight is on

if (book is "1984")
removeFromAllKindles()

Existential operator

believer = if aliens? then yes else no
console.log "I Believe" if believer

options ?= {}

options or= defaults

customer?.contactInfo?.emailAddress

Iterating Arrays using "in"

a = [1, 2, 3, 4, 5]
for val in a
doSomethingWith(val)

Loops return a value
a = [1, 2, 3, 4, 5]
timesTwo = for val in a
val * 2

=> [2, 4, 6, 8, 10 ]

Loops do not create scope..
countdown = [10..0]
for num in countdown
break if errorDetected()

if num is 0
console.log 'Blast-off!'
else
console.log "Aborted with #{num} seconds left!"

Iterating objects using "of"

for prop, val of someObject
# do something...

Iterating objects with "for
own" (hasOwnProperty)
Human = ->
Human::species = 'Homo-Sapiens'

ceo = new Human()
ceo.name = "Chris D'Agostino"
ceo.company = 'Near Infinity'
ceo.yearFounded = 2002

for own prop, val of ceo
console.log "#{prop} = #{val}"

What do vampires do while it's
dark?

while isDarkOutside()
suckBlood()

until isDayTime()
suckBlood()

Array Comprehensions

foods = ['pizza', 'soda', 'beer']

consume food for food in foods

consume food if food is 'beer' for food in foods

consume food for food in foods when food is 'beer'

nums = [1..10]

doubles = (n * 2 for n in nums)

squares = (n * n for n in nums)

evens = (n for n in nums when n % 2 is 0)

evensSquared = (n * n for n in evens)

Ripping things apart..

(a.k.a. de-structuring assignment)

[firstName, mi, lastName] = ['Wile', 'E', 'Coyote']

weatherReport = (location) ->
# Get the weather for real...
[location, 70, "Partly Cloudy"]

[city, temp, forecast] = weatherReport "Reston, VA"

fellowship =
maiar: ['Gandalf']
hobbits: ['Frodo', 'Sam', 'Merry', 'Pippin']
elves: ['Legolas']
dwarves: ['Gimli']
men: ['Aragorn', 'Boromir']

{hobbits: theHobbits, men: theMen} = fellowship

# or simply...

{hobbits, men} = fellowship

[sauce, toppings..., crust] = ['meat', 'pepperoni', 'banana
peppers', 'green peppers', 'thin']

console.log "Your pizza is a #{crust} crust with #{sauce}
sauce and #{toppings.join(', ')} on top"

spl at!

55

Functions are bound or unbound

Functions create scope

Variable declarations are pushed to the top of the
closest scope

Variables are not visible outside declared scope

weirdAl = function() {
a = a + 1;
// What's a's value at this point?
var a = 10;
return a;
}
result = weirdAl();

JavaScript

Scoping..
outer = 1 var changeNumbers, inner, outer;
changeNumbers = -> outer = 1;
inner = -1 changeNumbers = function() {
outer = 10 var inner;
inner = -1;
inner = changeNumbers()
return outer = 10;
};
inner = changeNumbers();

JavaScript

Example from: http://jashkenas.github.com/coffee-script/

Context is key.. but what is
this?

Bound function
setAnswer = (answer) -> @answer = answer
deepThought = {}
deepThought.setAnswer = setAnswer
deepThought.setAnswer 42
console.log deepThought.answer
=> 42

Applying context..
setAnswer = (answer) -> @answer = answer
deepThought = {}
setAnswer.apply deepThought, [ 42 ]
=> 42

Context via new..
Computer = (answer) ->
@answer = answer
deepThought = new Computer(42)
watson = new Computer("What is Toronto?")
=> 42

console.log watson.answer
=> "What is Toronto?"

Capturing this..
callback = (message) => @voicemail.push message

=> binds a function to the current scope

default arguments
selectMeals = (breakfast = 'Chick Fil A',
lunch = 'Macaroni Grill', dinner = 'Thai Noy') ->
"You chose #{breakfast}, #{lunch}, and #{dinner}"

console.log selectMeals("McDonald's", 'Subway', 'Outback')
=> You chose McDonald's, Subway, and Outback

console.log selectMeals(null, 'Subway', null)
=> You chose Chick Fil A, Subway, and Thai Noy

console.log selectMeals(null, null, null)
=> You chose Chick Fil A, Macaroni Grill, and Thai Noy

pizza = (sauce = 'tomato', toppings..., crust) ->
"A #{crust} pizza with #{sauce} sauce #{listOf(toppings)}"

console.log pizza('white', 'thin crust')
console.log pizza('tomato', 'pepperoni', 'pan')
console.log pizza(null, 'pepperoni', 'peppers', 'thin crust')

67

Prototypal inheritance
var Animal = function(name, species) {
this.name = name;
this.species = species;
}
Animal.prototype.eat = function(food) { ... }
Animal.prototype.sleep = function() { ... }
Animal.prototype.play = function() { ... }

var felix = new Animal('Felix', 'Feline');
felix.sleep();

var fido = new Animal('Fido', 'Canine');
fido.play();
fido.eat();
JavaScript

class Bike
constructor: (@brand) ->
@gear = 1

changeGear: (newGear) ->
@gear = newGear

currentGear: ->
@gear

status: ->
"#{@brand} cruising in gear #{@gear}"

class MtnBike extends Bike
changeGear: (newGear) ->
# do something special for mtn bikes...
super newGear

cruiser = new Bike("Schwinn")
cruiser.changeGear(4)
console.log cruiser.status()

mtn = new MtnBike("Specialized")
mtn.changeGear(8)
console.log mtn.status()

string interpolation

embedded JS using `...` (backticks)

switch/when/else

try/catch/ﬁnally

multi-line strings

enhanced regular expressions

Cake and Cakeﬁles

Other Considerations..
Debugging

Compilation

Deployment

Testing

"Because DHH says so..."

(yes, this is a joke)

CoffeeScript: Accelerated JavaScript Development
http://pragprog.com/titles/tbcoffee/coffeescript

CoffeeScript GitHub page
http://jashkenas.github.com/coffee-script/

http://lmgtfy.com/?q=coffeescript

photo attributions
Coffee # 1 -
http://www.flickr.com/photos/dyobmit/18588671/

Coffee # 2 -
http://www.flickr.com/photos/ibcbulk/86885289/

Python -
http://www.flickr.com/photos/lesmontsdore/5513104816/

Rip Apart Napkin -
http://www.flickr.com/photos/benreichelt/5543115344/

Weird Al - http://www.flickr.com/photos/schilder/4749864091/

Splat Wallpaper -
http://wallpaperstock.net/digital-splat_wallpapers_11732_1600x1200_1.html

Grab Bag -
http://www.flickr.com/photos/maynard/2126229821/

(others from iStockPhoto...)

(my info)

scott.leberknight@nearinfinity.com
www.nearinfinity.com/blogs/
twitter: sleberknight

CoffeeScript

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