This document provides an introduction to CoffeeScript for Node developers. It discusses that CoffeeScript is a programming language that compiles to JavaScript, providing syntactic sugar. It notes that CoffeeScript is mature and production-ready, having been initially released in 2009. It highlights companies like Dropbox and GitHub that use CoffeeScript. It provides examples of CoffeeScript syntax for functions, objects, classes, and more, and how they compile to JavaScript. It also discusses debugging CoffeeScript applications and CoffeeScript scoping.

1. COFFEESCRIPT
AN INTRODUCTION FOR NODE DEVELOPERS
BY: MEHDI VALIKHANI
SOFTWARE ENGINEER @ ALPHATISE
Follow me: @mehdivk |
mehdi@alphatise.com

2. IT'S JUST JAVASCRIPT
COFFEESCRIPT IS A PROGRAMMING LANGUAGE THAT
TRANSCOMPILES TO JAVASCRIPT.
SYNTACTIC SUGAR TO JAVASCRIPT

3. IT'S MATURE AND PRODUCTION-READY
DEVELOPED BY: JEREMY ASHKENAS
INITIAL COMMIT: DECEMBER 13TH, 2009
FIRST RELEASE: DECEMBER 24H, 2009
VERSION 1.0: FEBRUARY 2010
CURRENT VERSION: 1.8

4. WHO'S USING
COFFEESCRIPT?
DROPBOX
GITHUB

5. WRITE LESS, DO MORE
HUMAN-READABLE CODE
STAY AWAY FROM WEIRD JS BEHAVIOUR
SAY GOODBYE TO PROTOTYPE! USE CLASSES
ANY MANY MORE ...

6. COFFEESCRIPT SYNTAX

7. NO MORE VAR ; ( )
async = require 'async'
console.log async.VERSION
var async = require('async');
console.log(async.VERSION);

8. FUNCTIONS
IT'S PART OF OUR EVERYDAY LIFE IN JS WORLD
LET'S BE AGILE!

9. addUser = (user, cb) ->
model = new User
#DO SOMETHING
model.save (err, result) ->
cb null, result
var addUser = function(user, cb) {
var model = new User();
//DO SOMETHING
model.save(function(err, result){
cb(err, result);
});
}

10. IMPLICIT RETURN
someFunction = (param1, param2) ->
param1 * param2 * param2
console.log someFunction 100, 200
var someFunction;
someFunction = function(param1, param2) {
return param1 * param2 * param2;
}
console.log(someFunction(100, 200));

11. OBJECTS
GET RID OF THOSE { } ,
bus =
routeNumber: 273
from: 'Wynyard'
to: 'Chatswood'
via: 'North Sydney, Pacific Highway'
var bus = {
routerNumber: 273,
from: 'Wynyad',
to: 'Chatswood',
via: 'North Sydney, Pacific Highway'
}

12. query =
status:
$in: ['active', 'pending_for_approval']
payment:
$nin: ['invoice', 'free']
tc:
$exists: true
var query = {
status: {
$in: ['active', 'pending_for_approval']
},
payment: {
$nin: ['invoice', 'free']
},
tc: {
$exists: true
}
}

13. STRING INTERPOLOATION
meetup = 'Node'
msg = "#{meetup} meeup is awsome!"
console.log msg
var meetup = 'Node';
var msg = meetup + ' meetup is awsome!';
console.log(msg);

14. CLASSES
BETTER INHERITANCE WITHOUT PROTOTYPE
WE SHOULDN'T USE LIBRARIES TO HAVE CLASSES IN JS

15. class Cache
generateCacheKey: (key) ->
throw new Error 'Not Implemented'
getPeriod: ->
120 * 60
store: (key, data) ->
throw new Error 'Not Implemented'
clearCache: (key) ->
#DO SOMETHING
class RedisCache extends Cache
generateCacheKey: (key) ->
"redis_cache_#{key}"
store: (key, data) ->
period = @.getPeriod()
#STORE IN REDIS

16. DESTRUCTURING OBJECTS
{Router} = require 'express'
router = new Router
var express = require('express');
var Router = experss.Router;
router = new Router();

17. DESTRUCTURING ARRAYS
student = 'Mehdi Valikhani'
[firstName, lastName] = student.split ' '
var student, ref, firstName, lastName;
student = 'Mehdi Valikhani';
ref = student.split(' ');
firstName = ref[0];
lastName = ref[1];

18. DESTRUCTING ARGUMENTS
calculator = ({width, height}) ->
width * height
options =
width: 10
height: 5
alert calculator options

19. EXISTENTIAL OPERATOR ?
REMOVE THOSE NULL OR UNDEFINED CHECKES FROM CODE
if err?
#log to logger
cb err
if (typeof err !== "undefined" && err !== null)
//log to logger
cb(err);

20. INSTALL COFFEESCRIPT
npm install -g coffee-script

21. EXECUTE A SCRIPT
coffee /path/to/script.coffee

22. COMPILE A SCRIPT
coffee -c /path/to/script.coffee

23. NODE + COFFEE
FROM SCRATCH
REST API DEVELOPMENT USING EXPRESS + NODE + COFFEE

24. CODE STRUCTURE
+ lib
+ books
Book.coffee //Our Mongoose Model
router.coffee //router for books API
+ node_modules
+ body-parser //from JSON responses
+ coffee-script //compiler of Coffee files
+ express //express framework
app.coffee //express app config
package.json // NO DESCRIPTION
index.js //ACTUAL MAGIC HAPPENS HERE!

25. app.coffee
bodyParser = require 'body-parser'
express = require 'express'
userRouter = require './lib/books/router'
app = express()
app.use bodyParser.json()
app.use '/users', userRouter
module.exports = app

26. lib/books/router.coffee
{Router} = require 'express'
Book = require './Book'
router = new Router
fetchBook = (req, res, next) ->
req.paramBook = Book
next()
getBook = (req, res) ->
res.json(req.paramBook)
router.route('/:book_id')
.all(fetchBook)
.get(getBook)
module.exports = router

27. index.js
require('coffee-script/register');
var app = require('./app');
app.listen(1984, function(){
console.log('App is available via http://127.0.0.1:1984');
});

28. RUN THE APP
node index.js
nodemon -e js,coffee index.js

29. NODE + COFFEE
AN EXISTING PROJECT

30. ADD FOLLOWING CODE TO YOUR STARTER FILE
require('coffee-script/regiter');

31. THAT'S IT!
Add .coffee files, write your code in coffee
require other .js or .coffee files as always

32. RUN THE APP
node index.js
nodemon -e js,coffee index.js

33. DEBUGGING
COFFEESCRIPT
APPLICATIONS

34. USE "DEBUGGER" AS ALWAYS
fetchBook = (req, res, next) ->
debugger
req.paramBook = Book
next()
node debug index.js

35. BUT DON'T FORGET!
in debug mode, you will be faced with compiled
JS code
break in lib/books/router.coffee:11
9
10 fetchBook = function(req, res, next) {
11 debugger;
12 req.paramBook = Book;
13 return next();
debug> repl
Press Ctrl + C to leave debug repl
> req.params.book_id
'123'
>

36. JAVASCRIPT SCOPING
in JavaScript, the scope of a variable is
defined by its location within the source code
(it is apparent lexically) and nested
functions have access to variables declared in
their outer scope. - mozilla.org

37. Question: What's result of running this code?
name = 'Alex'
greeting = ->
name = 'James'
console.log "Hey #{name}!"
greeting()
console.log "Hey #{name}!"

38. A:
> Hey James!
> Hey James!
B:
> Hey James!
> Hey Alex!

39. "A" IS CORRECT ANSWER
> Hey James!
> Hey James!

40. THIS IS COMPILED-TO-JS VERSION OF ABOVE
CODE
var greeting, name;
name = 'Alex';
greeting = function() {
name = 'James';
return console.log("Hey " + name + "!");
};
greeting();
console.log("Hey " + name + "!");

41. TWO IMPORTANT FACTS
ABOUT COFEESCRIPT SCOPING
Variable shadowing is not allowed
variable is created at the moment of the first assignment to it

42. "VARIABLE SHADOWING IS NOT ALLOWED"
DOESN'T MEAN
YOU CAN'T DEFINE A VARIABLE MORE THAN
ONCE IN DIFFERENT FILES
IT MEANS
YOU CAN'T DEFINE IT MORE THAN ONCE IN A
SINGLE FILE

43. SO WHAT SHOULD I DO IF I WANT TO HAVE
SHADOWS?
It's not a good practice, don't do that!
It decreases readbility of your code!
Brings more confusion to your code
With shadowing you can't access our variables anymore (with
same name)

44. USE `` TO BRING VAR BACK
name = 'Alex'
greeting = ->
` var name
`
name = 'James'
console.log "Hey #{name}!"
greeting()
console.log "Hey #{name}!"
It a kind of hack! Don't do that!

45. SHADOW IT USING FUNCTION PARAMETER
name = 'Alex'
greeting = (name = '')->
name = 'James'
console.log "Hey #{name}!"
greeting()
console.log "Hey #{name}!"
Better first solution!

46. USE COFEESCRIPT'S CLOSURE FEATURE
This is much much better!
name = 'Alex'
greeting = ->
do (name = '') ->
name = 'James'
console.log "Hey #{name}!"
greeting()
console.log "Hey #{name}!"

47. MORE INFO ABOUT LEXICAL SCOPING:
https://github.com/raganwald-deprecated/
homoiconic/blob/master/2012/09/actually-YOU-dont-
understand-lexical-scope.md
https://github.com/raganwald-deprecated/
homoiconic/blob/master/2012/09/lexical-scope-in-
coffeescript.md

48. USEFUL RESOURCES
CoffeeScript Docs
Your best friend
CoffeeConsole: A Google Chrome Extention
Don't translate CoffeeScript to JS, try to learn as new langage
CoffeeScript Ristretto
Teaches CoffeeScript as new language instrad of translating to
JS
The Little Book On CoffeeScript
CoffeeScript Style Guide
Best Practices

49. Thank you!