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<%
require 'uv'
def code_for(file, executable=false)
@stripper ||= /(\A\(function\(\)\{\n|\}\)\(\);\Z|^ )/
return '' unless File.exists?("documentation/js/#{file}.js")
cs = File.read("documentation/cs/#{file}.cs")
js = File.read("documentation/js/#{file}.js").gsub(@stripper, '')
cshtml = Uv.parse(cs, 'xhtml', 'coffeescript', false, 'idle', false)
jshtml = Uv.parse(js, 'xhtml', 'javascript', false, 'idle', false)
append = executable == true ? '' : "alert(#{executable});"
run = executable == true ? 'run' : "run: #{executable}"
button = executable ? "<button onclick='javascript: #{js};#{append}'>#{run}</button>" : ''
"<div class='code'>#{cshtml}#{jshtml}#{button}<br class='clear' /></div>"
end
%>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html;charset=UTF-8" />
<title>CoffeeScript</title>
<link rel="stylesheet" type="text/css" href="documentation/css/docs.css" />
<link rel="stylesheet" type="text/css" href="documentation/css/idle.css" />
</head>
<body>
<div class="container">
<h1><sub style="font-size: 100px;">☕</sub> CoffeeScript</h1>
<p>
CoffeeScript is a little language that compiles into JavaScript. Think
of it as JavaScript's less ostentatious kid brother — the same genes,
roughly the same height, but a different sense of style. Apart from a handful of
bonus goodies, statements in CoffeeScript correspond one-to-one with their
equivalent in JavaScript, it's just another way of saying it.
</p>
<p>
<b>Disclaimer:</b>
CoffeeScript is just for fun and seriously alpha. I'm sure that there are still
plenty of holes in the lexer and leaks in the syntax. <i>There is no guarantee,
explicit or implied, of its suitability for any purpose.</i> That said,
it compiles into clean JavaScript (the good parts) that can use existing
JavaScript libraries seamlessly, and passes through
<a href="http://www.jslint.com/">JSLint</a> without warnings. The compiled
output is quite readable — pretty-printed, with comments
preserved intact.
</p>
<h2>Table of Contents</h2>
<p>
<a href="#overview">Mini Overview</a><br />
<a href="#installation">Installation and Usage</a><br />
<a href="#punctuation">Punctuation Primer</a><br />
<a href="#functions">Functions and Invocation</a><br />
<a href="#assignment">Assignment</a><br />
<a href="#objects_and_arrays">Objects and Arrays</a><br />
<a href="#lexical_scope">Lexical Scoping and Variable Safety</a><br />
<a href="#conditionals">Conditionals, Ternaries, and Conditional Assignment</a><br />
<a href="#expressions">Everything is an Expression</a><br />
<a href="#aliases">Aliases</a><br />
<a href="#while">While Loops</a><br />
<a href="#array_comprehensions">Array Comprehensions</a><br />
<a href="#slice">Array Slice Literals</a><br />
<a href="#inheritance">Inheritance, and Calling Super from a Subclass</a><br />
<a href="#embedded">Embedded JavaScript</a><br />
<a href="#switch">Switch/When/Else</a><br />
<a href="#try">Try/Catch/Finally</a><br />
<a href="#strings">Multiline Strings</a><br />
<a href="#contributing">Contributing</a><br />
<a href="#change_log">Change Log</a><br />
</p>
<h2 id="overview">Mini Overview</h2>
<p><i>CoffeeScript on the left, compiled JavaScript output on the right.</i></p>
<%= code_for('overview', 'cubed_list') %>
<h2 id="installation">Installation and Usage</h2>
<p>
The CoffeeScript compiler is written in pure Ruby, and is available
as a Ruby Gem.
</p>
<pre>
gem install coffee-script</pre>
<p>
Installing the gem provides the <tt>coffee-script</tt> command, which can
be used to compile CoffeeScript <tt>.cs</tt> files into JavaScript, as
well as debug them. In conjunction with
<a href="http://narwhaljs.org/">Narwhal</a>, the <tt>coffee-script</tt>
command also provides direct evaluation and an interactive REPL.
When compiling to JavaScript, <tt>coffee-script</tt> writes the output
as <tt>.js</tt> files in the same directory by default, but output
can be customized with the following options:
</p>
<table>
<tr>
<td width="25%"><code>-i, --interactive</code></td>
<td>
Launch an interactive CoffeeScript session.
Requires <a href="http://narwhaljs.org/">Narwhal</a>.
</td>
</tr>
<tr>
<td><code>-r, --run</code></td>
<td>
Compile and execute the CoffeeScripts without saving the intermediate
JavaScript. Requires <a href="http://narwhaljs.org/">Narwhal</a>.
</td>
</tr>
<tr>
<td><code>-o, --output [DIR]</code></td>
<td>
Write out all compiled JavaScript files into the specified directory.
</td>
</tr>
<tr>
<td><code>-w, --watch</code></td>
<td>
Watch the modification times of the coffee-scripts, recompiling as
soon as a change occurs.
</td>
</tr>
<tr>
<td><code>-p, --print</code></td>
<td>
Instead of writing out the JavaScript as a file, print it
directly to <b>stdout</b>.
</td>
</tr>
<tr>
<td><code>-l, --lint</code></td>
<td>
If the <tt>jsl</tt> (JavaScript Lint) command is installed, use it
to check the compilation of a CoffeeScript file. (Handy in
conjunction with <tt>--watch</tt>)
</td>
</tr>
<tr>
<td><code>-e, --eval</code></td>
<td>
Compile and print a little snippet of CoffeeScript directly from the
command line (or from <b>stdin</b>). For example:<br /><tt>coffee-script -e "square: x => x * x."</tt>
</td>
</tr>
<tr>
<td><code>-t, --tokens</code></td>
<td>
Instead of parsing the CoffeeScript, just lex it, and print out the
token stream: <tt>[:IDENTIFIER, "square"], [":", ":"], [:PARAM, "x"]</tt> ...
</td>
</tr>
<tr>
<td><code>-v, --verbose</code></td>
<td>
As the JavaScript is being generated, print out every step of code
generation, including lexical scope and the node in the
AST.
</td>
</tr>
<tr>
<td><code>-n, --no-wrap</code></td>
<td>
Compile the JavaScript without the top-level function safety wrapper
or var declarations, for situations where you want to add every
variable to global scope.
</td>
</tr>
<tr>
<td><code>--install-bundle</code></td>
<td>
Install the TextMate bundle for CoffeeScript syntax highlighting.
</td>
</tr>
</table>
<p>
<b>Examples:</b>
</p>
<pre>
coffee-script path/to/script.cs
coffee-script --watch --lint experimental.cs
coffee-script --print app/scripts/*.cs > concatenation.js</pre>
<h2>Language Reference</h2>
<p>
<i>
This reference is structured so that it can be read from top to bottom,
if you like. Later sections use ideas and syntax previously introduced.
Familiarity with JavaScript is assumed.
In all of the following examples, the source CoffeeScript is provided on
the left, and the direct compilation into JavaScript is on the right.
</i>
</p>
<p id="punctuation">
<b class="header">Punctuation Primer</b>
You don't need to use semicolons <tt>;</tt> to terminate expressions, ending
the line will do just as well. All other whitespace is
not significant. Instead of using curly braces <tt>{ }</tt>
to delimit a block of code, use a period <tt>.</tt> to mark the end of a
block, for
<a href="#functions">functions</a>,
<a href="#conditionals">if-statements</a>,
<a href="#switch">switch</a>, and <a href="#try">try/catch</a>.
</p>
<p id="functions">
<b class="header">Functions and Invocation</b>
Functions are defined by a list of parameters, an arrow, and the
function body. The empty function looks like this: <tt>=>.</tt>
</p>
<%= code_for('functions', 'cube(5)') %>
<p id="assignment">
<b class="header">Assignment</b>
Use a colon <tt>:</tt> to assign, as in
<a href="http://json.org">JSON</a>. Equal signs are only needed for
mathy things.
</p>
<%= code_for('assignment', 'greeting') %>
<p id="objects_and_arrays">
<b class="header">Objects and Arrays</b>
Object and Array literals look very similar to their JavaScript cousins.
When you spread out each assignment on a separate line, the commas are
optional. In this way, assigning object properties looks the same as
assigning local variables.
</p>
<%= code_for('objects_and_arrays', 'song.join(",")') %>
<p id="lexical_scope">
<b class="header">Lexical Scoping and Variable Safety</b>
The CoffeeScript compiler takes care to make sure that all of your variables
are properly declared within lexical scope — you never need to write
<tt>var</tt> yourself.
</p>
<%= code_for('scope', 'new_num') %>
<p>
Notice how the variables are declared with <tt>var</tt> the first time
they appear. The second reference of <b>num</b>, within the function,
is not redeclared because <b>num</b> is still in scope. As opposed
to the second occurrence of <b>new_num</b>, in the last line.
</p>
<p>
Although suppressed within this documentation for clarity, all
CoffeeScript output is wrapped in an anonymous function:
<tt>(function(){ ... })();</tt> This safety wrapper, combined with the
automatic generation of the <tt>var</tt> keyword, make it exceedingly difficult
to pollute the global namespace by accident.
</p>
<p id="conditionals">
<b class="header">Conditionals, Ternaries, and Conditional Assignment</b>
<b>If/else</b> statements can be written without the use of parenthesis and
curly brackets. As with functions and other block expressions, conditionals
are closed with periods. No period is necessary when using the single-line
postfix form, with the <tt>if</tt> at the end.
</p>
<p>
CoffeeScript will compile <b>if</b> statements using the ternary operator
when possible, to make it easier to use the result as an expression.
</p>
<%= code_for('conditionals') %>
<p>
The conditional assignment operators are available: <tt>||:</tt>,
which only assigns a value to a variable if the variable's current value
is falsy, and <tt>&&:</tt>, which only replaces the value of
truthy variables.
</p>
<p id="expressions">
<b class="header">Everything is an Expression (at least, as much as possible)</b>
You might have noticed how even though we don't add return statements
to CoffeeScript functions, they nonetheless return their final value.
The CoffeeScript compiler tries to make sure that all statements in the
language can be used as expressions. Watch how the <tt>return</tt> gets
pushed down into each possible branch of execution, in the function
below.
</p>
<%= code_for('expressions', 'eldest') %>
<p>
The same mechanism is used to push down assignment through <b>switch</b>
statements, and <b>if-elses</b> (although the ternary operator is preferred).
</p>
<p id="aliases">
<b class="header">Aliases</b>
Because the <tt>==</tt> operator frequently causes undesirable coercion,
is intransitive, and has a different meaning than in other languages,
CoffeeScript compiles <tt>==</tt> into <tt>===</tt>, and <tt>!=</tt> into
<tt>!==</tt>.
In addition, <tt>is</tt> compiles into <tt>===</tt>,
and <tt>isnt</tt> into <tt>!==</tt>.
</p>
<p>
You can use <tt>not</tt> as an alias for <tt>!</tt>.
</p>
<p>
For logic, <tt>and</tt> compiles to <tt>&&</tt>, and <tt>or</tt>
into <tt>||</tt>.
</p>
<p>
Instead of a newline or semicolon, <tt>then</tt> can be used to separate
conditions from expressions, in <b>while</b>,
<b>if</b>/<b>else</b>, and <b>switch</b>/<b>when</b> statements.
</p>
<p>
As in <a href="http://yaml.org/">YAML</a>, <tt>on</tt> and <tt>yes</tt>
are the same as boolean <tt>true</tt>, while <tt>off</tt> and <tt>no</tt> are boolean <tt>false</tt>.
</p>
<p>
For single-line statements, <tt>unless</tt> can be used as the inverse of <tt>if</tt>.
</p>
<%= code_for('aliases') %>
<p id="while">
<b class="header">While Loops</b>
The only low-level loop that CoffeeScript provides is the while loop.
</p>
<%= code_for('while') %>
<p>
Other JavaScript loops, such as <b>for</b> loops and <b>do-while</b> loops
can be mimicked by variations on <b>while</b>, but the hope is that you
won't need to do that with CoffeeScript, either because you're using
<b>each</b> (<b>forEach</b>) style iterators, or...
</p>
<p id="array_comprehensions">
<b class="header">Array Comprehensions</b>
For your looping needs, CoffeeScript provides array comprehensions
similar to Python's. They replace (and compile into) <b>for</b> loops, with
optional guard clauses and the value of the current array index.
Unlike for loops, array comprehensions are expressions, and can be returned
and assigned. They should be able to handle most places where you otherwise
would use a loop, <b>each</b>/<b>forEach</b>, <b>map</b>, or <b>select</b>/<b>filter</b>.
</p>
<%= code_for('array_comprehensions') %>
<p id="slice">
<b class="header">Array Slice Literals</b>
CoffeeScript includes syntax for extracting slices of arrays.
The first argument is the index of the first element in the slice, and
the second is the index of the last one.
</p>
<%= code_for('slices', 'three_to_six') %>
<p id="inheritance">
<b class="header">Inheritance, and Calling Super from a Subclass</b>
JavaScript's prototypal inheritance has always been a bit of a
brain-bender, with a whole family tree of libraries that provide a cleaner
syntax for classical inheritance on top of JavaScript's prototypes:
<a href="http://code.google.com/p/base2/">Base2</a>,
<a href="http://prototypejs.org/">Prototype.js</a>,
<a href="http://jsclass.jcoglan.com/">JS.Class</a>, etc.
The libraries provide syntactic sugar, but the built-in inheritance would
be completely usable if it weren't for a couple of small exceptions:
it's awkward to call <b>super</b> (the prototype object's
implementation of the current function), and it's awkward to correctly
set the prototype chain. CoffeeScript provides <tt>extends</tt>
to help with prototype setup, and converts
<tt>super()</tt> calls into calls against the immediate ancestor's
method of the same name.
</p>
<%= code_for('super', true) %>
<p id="embedded">
<b class="header">Embedded JavaScript</b>
If you ever need to interpolate literal JavaScript snippets, you can
use backticks to pass JavaScript straight through.
</p>
<%= code_for('embedded', 'hi()') %>
<p id="switch">
<b class="header">Switch/When/Else</b>
<b>Switch</b> statements in JavaScript are rather broken. You can only
do comparisons based on string equality, and need to remember to <b>break</b> at the end of
every <b>case</b> statement to avoid accidentally falling through to
the default case. CoffeeScript compiles <b>switch</b> statements into JavaScript if-else chains, allowing you to
compare any object (via <b>===</b>), preventing fall-through, and resulting
in a returnable, assignable expression. The format is: <tt>switch</tt> condition,
<tt>when</tt> clauses, <tt>else</tt> the default case.
</p>
<%= code_for('switch') %>
<p id="try">
<b class="header">Try/Catch/Finally</b>
Try/catch statements are just about the same as JavaScript (although
they work as expressions).
</p>
<%= code_for('try') %>
<p id="try">
<b class="header">Multiline Strings</b>
Multiline strings are allowed in CoffeeScript.
</p>
<%= code_for('strings', 'moby_dick') %>
<h2 id="contributing">Contributing</h2>
<p>
Here's a wish list of things that would be wonderful to have in
CoffeeScript:
</p>
<ul>
<li>
A JavaScript version of the compiler, perhaps using Alessandro Warth's
<a href="http://tinlizzie.org/ometa/">OMeta</a>.
</li>
<li>
Ideas for alternate syntax to end blocks of expressions — the periods
can look a little weird with deeply nested structure.
</li>
<li>
Test cases for any syntax errors you encounter that you think CoffeeScript
should be able to compile properly.
</li>
<li>
A tutorial that introduces CoffeeScript from the ground up for folks
without knowledge of JavaScript.
</li>
<li>
Integration with Processing.js's JavaScript API (this would depend on
having a JavaScript version of the compiler).
</li>
<li>
A lot of the code generation in <tt>nodes.rb</tt> gets into messy
string manipulation. Techniques for cleaning this up across the board
would be appreciated.
</li>
</ul>
<h2 id="change_log">Change Log</h2>
<p>
<b class="header" style="margin-top: 20px;">0.1.3</b>
The <tt>coffee-script</tt> command now includes <tt>--interactive</tt>,
which launches an interactive CoffeeScript session, and <tt>--run</tt>,
which directly compiles and executes a script. Both options depend on a
working installation of Narwhal.
The <tt>aint</tt> keyword has been replaced by <tt>isnt</tt>, which goes
together a little smoother with <tt>is</tt>.
Quoted strings are now allowed as identifiers within object literals: eg.
<tt>{"5+5": 10}</tt>.
All assignment operators now use a colon: <tt>+:</tt>, <tt>-:</tt>,
<tt>*:</tt>, etc.
</p>
<p>
<b class="header" style="margin-top: 20px;">0.1.2</b>
Fixed a bug with calling <tt>super()</tt> through more than one level of
inheritance, with the re-addition of the <tt>extends</tt> keyword.
Added experimental <a href="http://narwhaljs.org/">Narwhal</a>
support (as a Tusk package), contributed by
<a href="http://tlrobinson.net/">Tom Robinson</a>, including
<b>bin/cs</b> as a CoffeeScript REPL and interpreter.
New <tt>--no-wrap</tt> option to suppress the safety function
wrapper.
</p>
<p>
<b class="header" style="margin-top: 20px;">0.1.1</b>
Added <tt>instanceof</tt> and <tt>typeof</tt> as operators.
</p>
<p>
<b class="header" style="margin-top: 20px;">0.1.0</b>
Initial CoffeeScript release.
</p>
</div>
</body>
</html>