COFFEESCRIPT INTRODUCTION

To install CoffeeScript, use the following command in your console.

npm install -g coffee-script

.. or you can download it from:

https://github.com/jashkenas/coffeescript

Variables

In CoffeeScript there are :

• No variable declarations
• No semicolons

Take a look at the following code snippet:

CoffeeScript

message = "Ready for some Coffee?"
alert(message)

This will compile into the following JavaScript file:

JavaScript

var message;
message = 'Ready for some Coffee?';
alert(message);

There are 2 ways to create functions in JavaScript:

• Named Functions

function coffee() {
    return confirm("Ready for some Coffee?");
}

• Function Expressions

var coffee = function () {
  return confirm('Ready for some Coffee?');
};

In CoffeeScript, it's written with the following syntax:

code coffee();

But in CoffeeScript, we only use **Function Expressions.**

**CoffeeScript**

coffee = -> confirm "Ready for some Coffee?"

**JavaScript**

```js
var coffee = function() {
    return confirm("Ready for some Coffee?");
}

1 tab or 2 spaces indented -> converts to function() { Always has a return value

Returning a String

The following highlighted expressions is similar to:

"Your answer is #{answer}"

CoffeeScript

coffee = ->
    answer = confirm "Ready for some Coffee?"
    "Your answer is " + answer

JavaScript

var coffee;
coffee = function () {
  var answer;
  answer = confirm('Ready for some Coffee?');
  return 'Your answer is ' + answer;
};

Function Parameters

With CoffeeScript functions, you should use parenthesis on everything but the outermost call.

CoffeeScript

coffee = (message) ->
    answer = confirm message
    "Your answer is #{answer}"

alert coffee("Ready for some Coffee?")

Optinal Parameters

If we want a default message, we can assign it to the argument as below:

CoffeeScript

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

JavaScript

var coffee;
coffee = function (message) {
  var answer;
  if (message == null) {
    message = 'Ready for some Coffee?';
  }
  answer = confirm(message);
  return 'Your answer is ' + answer;
};

The CoffeeScript Compiler (optional)

You can optionally use a CoffeeScript Compiler to compile your code into JavaScript.

• Install Node.js
• Install npm
• Run $ npm install -g coffee-script

Here are few Command-Line examples, you can use:

Creates test.js

coffee -c test.coffee

Every time test.coffee is updated re-compile.

coffee -cw test.coffee

Compile all .coffee files in the src dir into the js dir.

coffee -c src -o js

Every time a file is updated re-compile.

coffee -wc src -o js