• Least amount of code to solve problems
• Readable and Understandable
• Easy to Maintain

• JavaScript's less ostentatious kid brother
• one-to-one with JavaScript
• better functional syntax
• compiles to the good parts

• Install Node.js
• Install npm

• npm install -g coffee-script
            

        coffee -h
        Usage: coffee [options] path/to/script.coffee -- [args]

          -b, --bare         compile without a top-level function wrapper
          -c, --compile      compile to JavaScript and save as .js files
          -e, --eval         pass a string from the command line as input
          -h, --help         display this help message
          -i, --interactive  run an interactive CoffeeScript REPL
          -j, --join         concatenate the source CoffeeScript before compiling
          -l, --lint         pipe the compiled JavaScript through JavaScript Lint
          -n, --nodes        print out the parse tree that the parser produces
              --nodejs       pass options directly to the "node" binary
          -o, --output       set the output directory for compiled JavaScript
          -p, --print        print out the compiled JavaScript
          -r, --require      require a library before executing your script
          -s, --stdio        listen for and compile scripts over stdio
          -t, --tokens       print out the tokens that the lexer/rewriter produce
          -v, --version      display the version number
          -w, --watch        watch scripts for changes and rerun commands
      

        $ coffee -c path/to/script.coffee

        $ coffee --watch experimental.coffee

        $ coffee --print *.coffee > all.js
      

        someText = "Hello folks!"
        alert someText
      

        var someText;
        someText = "Hello folks!";
        alert(someText);
      

• No variable declarations
• No semicolons

        if ViktorTsoi?
          alert "I know it!"
      

or

        alert "I know it!" if ViktorTsoi?
      

converted

        if (typeof ViktorTsoi !== "undefined" && ViktorTsoi !== null) {
          alert("I know it!");
        }
      

• Named Functions

              function oneCoffee() {
                return alert("One coffee ready!");
              }
            

• Function Expressions

              var oneCoffee = function() {
                return alert("One coffee ready!");
              }
            

        oneCoffee = ->
          alert "One coffee ready!"
      

or

        oneCoffee = -> alert "One coffee ready!"
      

converted

        var oneCoffee;
        oneCoffee = function() {
          return alert("One coffee ready!");
        };
      

  oneCoffee = (msg = "Ready for some Coffee?") ->
   answer = confirm msg
   "Your answer is #{answer}"
        

  var oneCoffee;
  oneCoffee = function(msg) {
    var answer;
    if (msg == null) {
      msg = "Ready for some Coffee?";
    }
    answer = confirm(msg);
    return "Your answer is " + answer;
  };
        

    square = (x) -> x * x

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

    var area, square;

    square = function(x) {
      return x * x;
    };

    area = function(x, y) {
      return x * y;
    };
        

if age < 18
  alert "Under age"
else
  alert "of age"
      

if age < 18 then alert 'Under age' else alert 'of age'
      

  
if (age < 18) {
  alert("Under age");
} else {
  alert("of age");
}
      

        
if 2 < newLevel < 5
  alert "In Range!"
      

        
if ((2 < newLevel && newLevel < 5)) {
  alert("In Range!");
}
      

fruit = ['apple', 'pear', 'orange']
fruit = [
  'apple'
  'pear'
  'orange'
]
      

var fruit;

fruit = ['apple', 'pear', 'orange'];

fruit = ['apple', 'pear', 'orange'];
      

  fruit = ['apple', 'pear', 'orange']
  for fr in fruit
    alert "Fruit: #{fr}"
  alert "Fruit: #{fr}" for fr in fruit
      

        
  var fr, fruit, _i, _j, _len, _len1;

  fruit = ['apple', 'pear', 'orange'];

  for (_i = 0, _len = fruit.length; _i < _len; _i++) {
    fr = fruit[_i];
    alert("Fruit: " + fr);
  }
  ...
      

  fruit = ['apple', 'pear', 'orange']
  withoutApple = (name for name in fruit when name isnt "apple")
      

  var fruit, name, withoutApple;
  fruit = ['apple', 'pear', 'orange'];
  withoutApple = (function() {
    var _i, _len, _results;
    _results = [];
    for (_i = 0, _len = fruit.length; _i < _len; _i++) {
      name = fruit[_i];
      if (name !== "apple") {
        _results.push(name);
      }
    }
    return _results;
  })();
      

  race = (winner, runners...) ->
    print winner, runners
      

  var race,
    __slice = [].slice;

  race = function() {
    var runners, winner;
    winner = arguments[0], runners = 2 <= arguments.length ? __slice.call(arguments, 1) : [];
    return print(winner, runners);
  };
      

"#{coffee} has #{attrs.in_stock}" for coffee, attrs of coffees
      

var attrs, coffee;

for (coffee in coffees) {
  attrs = coffees[coffee];
  "" + coffee + " has " + attrs.in_stock;
}
      

  class Base
    constructor: (@name) ->
    eat: (count) ->
      alert "I eat #{count} #{@name}"

  base = new Base("apple")
  base.eat(5)
      

  class Base
    constructor: (@name) ->
    eat: (count) =>
      alert "I eat #{count} #{@name}"
    notEat: =>
      $.ajax
        url: "some url"
        success: (data) =>
          @eat(data)
      

  class Base
    constructor: (@name) ->
    eat: (count) =>
      alert "I eat #{count} #{@name}"

  class Apple extends Base
    constructor: (@name) ->
    eat: (count) =>
      alert "Apple method"
      super(count)
      

  String::dasherize = ->
    this.replace /_/g, "-"
    
  alert "one_two".dasherize()
      

  String.prototype.dasherize = function() {
    return this.replace(/_/g, "-");
  };

  alert("one_two".dasherize());
      

  doSomething "123"
    
  doSomething # <- invalid
      

  doSomething("123");

  doSomething;
      

action = (token, i) ->
      @tokens.splice i, 0, @generate 'CALL_END', ')', token[2]
      

var action;

action = function(token, i) {
  return this.tokens.splice(i, 0, this.generate('CALL_END', ')', token[2]));
};
      

  action({key: value}, {option: value}, otherValue);
      

  action(key: value, option: value, otherValue)
      

  action({
    key: value,
    option: value
  }, otherValue);
      

  js = (parser.parse lexer.tokenize code).compile options
      

  var js;

  js = (parser.parse(lexer.tokenize(code))).compile(options);