coffeescript.txt

Coffeescript notes

Installation:

brew update
brew install node

Within .bashrc:
  export NODE_PATH=/usr/local/lib/node

npm install -g coffee-script

Check that it worked:

node -v
npm -v
coffee -v

======================================================================

Things I don't fully understand

apply and call

  run = (f, args...) -> f(args...)
  run2 = (f, args...) -> f.apply this, args
  run3 = (f, args...) -> f.call this, args...
  add = (a, b) -> a+b
  console.log run add, -1, 3
  console.log run2 add, -1, 3
  console.log run3 add, -1, 3

splice

  clearArray = (arr) ->
    arr.splice 0, arr.length
    return
  x = [5, 3, 2]
  console.log x
  clearArray x
  console.log x


-----

# copying arrays
a = [1,2,3]
b = a
c = a.slice(0)
a is b
not (a is c)

# sort strings as numbers
a = ['1', '12', '21', '3', '4']
a.sort((a,b) -> a-b)

# reduce, for summing an array
a = ['1', '12', '21', '3', '4']
a.reduce (t,s) -> Number(t) + Number(s)
a.map((d) -> Number(d)).reduce((t,s) -> t+s)

# create regular expression from a variable
ext = 'txt'
re = new RegExp("\.#{ext}$")
"blah.txt".match(re)

# list comprehensions for object
x = {a:1, b:2}
"#{k}: #{v}" for k,v of x
k for k of x
v for k,v of x

# create from prototype
y = Object.create x
y.d = 3
x.c = 4
k for k of y
k for own k of y # note use of "own"

# Multi-line strings
# (in REPL, use ctrl-v to switch between multi-line entry and not)
x = """blah blah blah
this is a multiline string
blah blah"""
# becomes 'blah blah blah\nthis is a multiline string\nblah blah'
# (also need ctrl-v for general code, like loops, that will need multiple lines)

# Again: for continuation lines (multiline code in the REPL)
# type ctrl-v (and then again ctrl-v to exit)

# delete element from hash
x = {a:1, b:2, c:3}
delete(x.b)

# another list comprehension example
z = ({x:Math.random(), y:Math.random()} for i in [1..20])