511 lines
20 KiB
Plaintext
511 lines
20 KiB
Plaintext
<%
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require 'uv'
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def code_for(file, executable=false)
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@stripper ||= /(\A\(function\(\)\{\n|\}\)\(\);\Z|^ )/
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return '' unless File.exists?("documentation/js/#{file}.js")
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cs = File.read("documentation/coffee/#{file}.coffee")
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js = File.read("documentation/js/#{file}.js").gsub(@stripper, '')
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cshtml = Uv.parse(cs, 'xhtml', 'coffeescript', false, 'idle', false)
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jshtml = Uv.parse(js, 'xhtml', 'javascript', false, 'idle', false)
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append = executable == true ? '' : "alert(#{executable});"
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run = executable == true ? 'run' : "run: #{executable}"
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button = executable ? "<button onclick='javascript: #{js};#{append}'>#{run}</button>" : ''
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"<div class='code'>#{cshtml}#{jshtml}#{button}<br class='clear' /></div>"
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end
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%>
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<!DOCTYPE html>
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<html>
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<head>
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<meta http-equiv="content-type" content="text/html;charset=UTF-8" />
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<title>CoffeeScript</title>
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<link rel="stylesheet" type="text/css" href="documentation/css/docs.css" />
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<link rel="stylesheet" type="text/css" href="documentation/css/idle.css" />
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</head>
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<body>
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<div class="container">
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<h1><sub style="font-size: 100px;">☕</sub> CoffeeScript</h1>
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<p>
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CoffeeScript is a little language that compiles into JavaScript. Think
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of it as JavaScript's less ostentatious kid brother — the same genes,
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roughly the same height, but a different sense of style. Apart from a handful of
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bonus goodies, statements in CoffeeScript correspond one-to-one with their
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equivalent in JavaScript, it's just another way of saying it.
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</p>
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<p>
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<b>Disclaimer:</b>
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CoffeeScript is just for fun and seriously alpha. I'm sure that there are still
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plenty of holes in the lexer and leaks in the syntax. <i>There is no guarantee,
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explicit or implied, of its suitability for any purpose.</i> That said,
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it compiles into clean JavaScript (the good parts) that can use existing
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JavaScript libraries seamlessly, and passes through
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<a href="http://www.jslint.com/">JSLint</a> without warnings. The compiled
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output is quite readable — pretty-printed, with comments
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preserved intact.
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</p>
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<h2>Table of Contents</h2>
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<p>
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<a href="#overview">Mini Overview</a><br />
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<a href="#installation">Installation and Usage</a><br />
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<a href="#punctuation">Punctuation Primer</a><br />
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<a href="#functions">Functions and Invocation</a><br />
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<a href="#assignment">Assignment</a><br />
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<a href="#objects_and_arrays">Objects and Arrays</a><br />
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<a href="#lexical_scope">Lexical Scoping and Variable Safety</a><br />
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<a href="#conditionals">Conditionals, Ternaries, and Conditional Assignment</a><br />
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<a href="#expressions">Everything is an Expression</a><br />
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<a href="#aliases">Aliases</a><br />
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<a href="#while">While Loops</a><br />
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<a href="#array_comprehensions">Array Comprehensions</a><br />
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<a href="#slice">Slicing Arrays with Ranges</a><br />
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<a href="#inheritance">Inheritance, and Calling Super from a Subclass</a><br />
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<a href="#embedded">Embedded JavaScript</a><br />
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<a href="#switch">Switch/When/Else</a><br />
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<a href="#try">Try/Catch/Finally</a><br />
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<a href="#strings">Multiline Strings</a><br />
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<a href="#contributing">Contributing</a><br />
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<a href="#change_log">Change Log</a><br />
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</p>
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<h2 id="overview">Mini Overview</h2>
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<p><i>CoffeeScript on the left, compiled JavaScript output on the right.</i></p>
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<%= code_for('overview', 'cubed_list') %>
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<h2 id="installation">Installation and Usage</h2>
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<p>
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The CoffeeScript compiler is written in pure Ruby, and is available
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as a Ruby Gem.
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</p>
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<pre>
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gem install coffee-script</pre>
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<p>
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Installing the gem provides the <tt>coffee</tt> command, which can
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be used to compile CoffeeScript <tt>.coffee</tt> files into JavaScript, as
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well as debug them. In conjunction with
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<a href="http://narwhaljs.org/">Narwhal</a>, the <tt>coffee</tt>
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command also provides direct evaluation and an interactive REPL.
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When compiling to JavaScript, <tt>coffee</tt> writes the output
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as <tt>.js</tt> files in the same directory by default, but output
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can be customized with the following options:
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</p>
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<table>
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<tr>
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<td width="25%"><code>-i, --interactive</code></td>
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<td>
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Launch an interactive CoffeeScript session.
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Requires <a href="http://narwhaljs.org/">Narwhal</a>.
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</td>
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</tr>
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<tr>
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<td><code>-r, --run</code></td>
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<td>
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Compile and execute the CoffeeScripts without saving the intermediate
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JavaScript. Requires <a href="http://narwhaljs.org/">Narwhal</a>.
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</td>
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</tr>
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<tr>
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<td><code>-o, --output [DIR]</code></td>
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<td>
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Write out all compiled JavaScript files into the specified directory.
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</td>
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</tr>
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<tr>
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<td><code>-w, --watch</code></td>
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<td>
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Watch the modification times of the coffee-scripts, recompiling as
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soon as a change occurs.
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</td>
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</tr>
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<tr>
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<td><code>-p, --print</code></td>
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<td>
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Instead of writing out the JavaScript as a file, print it
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directly to <b>stdout</b>.
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</td>
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</tr>
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<tr>
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<td><code>-l, --lint</code></td>
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<td>
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If the <tt>jsl</tt> (JavaScript Lint) command is installed, use it
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to check the compilation of a CoffeeScript file. (Handy in
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conjunction with <tt>--watch</tt>)
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</td>
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</tr>
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<tr>
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<td><code>-e, --eval</code></td>
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<td>
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Compile and print a little snippet of CoffeeScript directly from the
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command line (or from <b>stdin</b>). For example:<br /><tt>coffee -e "square: x => x * x."</tt>
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</td>
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</tr>
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<tr>
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<td><code>-t, --tokens</code></td>
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<td>
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Instead of parsing the CoffeeScript, just lex it, and print out the
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token stream: <tt>[:IDENTIFIER, "square"], [":", ":"], [:PARAM, "x"]</tt> ...
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</td>
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</tr>
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<tr>
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<td><code>-v, --verbose</code></td>
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<td>
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As the JavaScript is being generated, print out every step of code
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generation, including lexical scope and the node in the
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AST.
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</td>
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</tr>
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<tr>
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<td><code>-n, --no-wrap</code></td>
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<td>
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Compile the JavaScript without the top-level function safety wrapper
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or var declarations, for situations where you want to add every
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variable to global scope.
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</td>
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</tr>
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<tr>
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<td><code>--install-bundle</code></td>
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<td>
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Install the TextMate bundle for CoffeeScript syntax highlighting.
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</td>
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</tr>
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</table>
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<p>
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<b>Examples:</b>
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</p>
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<pre>
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coffee path/to/script.coffee
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coffee --interactive
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coffee --watch --lint experimental.coffee
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coffee --print app/scripts/*.coffee > concatenation.js</pre>
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<h2>Language Reference</h2>
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<p>
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<i>
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This reference is structured so that it can be read from top to bottom,
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if you like. Later sections use ideas and syntax previously introduced.
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Familiarity with JavaScript is assumed.
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In all of the following examples, the source CoffeeScript is provided on
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the left, and the direct compilation into JavaScript is on the right.
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</i>
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</p>
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<p id="punctuation">
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<b class="header">Punctuation Primer</b>
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You don't need to use semicolons <tt>;</tt> to terminate expressions, ending
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the line will do just as well. All other whitespace is
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not significant. Instead of using curly braces <tt>{ }</tt>
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to delimit a block of code, use a period <tt>.</tt> to mark the end of a
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block, for
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<a href="#functions">functions</a>,
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<a href="#conditionals">if-statements</a>,
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<a href="#switch">switch</a>, and <a href="#try">try/catch</a>.
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</p>
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<p id="functions">
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<b class="header">Functions and Invocation</b>
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Functions are defined by a list of parameters, an arrow, and the
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function body. The empty function looks like this: <tt>=>.</tt>
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</p>
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<%= code_for('functions', 'cube(5)') %>
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<p id="assignment">
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<b class="header">Assignment</b>
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Use a colon <tt>:</tt> to assign, as in
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<a href="http://json.org">JSON</a>. Equal signs are only needed for
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mathy things.
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</p>
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<%= code_for('assignment', 'greeting') %>
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<p>
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Declarations of new variables are pushed up to the top of the current scope,
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so that assignments may always be used within expressions.
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</p>
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<p id="objects_and_arrays">
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<b class="header">Objects and Arrays</b>
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Object and Array literals look very similar to their JavaScript cousins.
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When you spread out each assignment on a separate line, the commas are
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optional. In this way, assigning object properties looks the same as
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assigning local variables.
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</p>
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<%= code_for('objects_and_arrays', 'song.join(",")') %>
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<p id="lexical_scope">
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<b class="header">Lexical Scoping and Variable Safety</b>
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The CoffeeScript compiler takes care to make sure that all of your variables
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are properly declared within lexical scope — you never need to write
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<tt>var</tt> yourself.
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</p>
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<%= code_for('scope', 'new_num') %>
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<p>
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Notice how the variables are declared with <tt>var</tt> the first time
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they appear. The second reference of <b>num</b>, within the function,
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is not redeclared because <b>num</b> is still in scope. As opposed
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to the second occurrence of <b>new_num</b>, in the last line.
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</p>
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<p>
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Although suppressed within this documentation for clarity, all
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CoffeeScript output is wrapped in an anonymous function:
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<tt>(function(){ ... })();</tt> This safety wrapper, combined with the
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automatic generation of the <tt>var</tt> keyword, make it exceedingly difficult
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to pollute the global namespace by accident.
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</p>
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<p id="conditionals">
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<b class="header">Conditionals, Ternaries, and Conditional Assignment</b>
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<b>If/else</b> statements can be written without the use of parenthesis and
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curly brackets. As with functions and other block expressions, conditionals
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are closed with periods. No period is necessary when using the single-line
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postfix form, with the <tt>if</tt> at the end.
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</p>
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<p>
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CoffeeScript will compile <b>if</b> statements using the ternary operator
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when possible, to make it easier to use the result as an expression.
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</p>
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<%= code_for('conditionals') %>
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<p>
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The conditional assignment operators are available: <tt>||=</tt>,
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which only assigns a value to a variable if the variable's current value
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is falsy, and <tt>&&=</tt>, which only replaces the value of
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truthy variables.
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</p>
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<p id="expressions">
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<b class="header">Everything is an Expression (at least, as much as possible)</b>
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You might have noticed how even though we don't add return statements
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to CoffeeScript functions, they nonetheless return their final value.
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The CoffeeScript compiler tries to make sure that all statements in the
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language can be used as expressions. Watch how the <tt>return</tt> gets
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pushed down into each possible branch of execution, in the function
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below.
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</p>
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<%= code_for('expressions', 'eldest') %>
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<p>
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The same mechanism is used to push down assignment through <b>switch</b>
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statements, and <b>if-elses</b> (although the ternary operator is preferred).
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Another part of manipulating assignment statements is
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CoffeeScript's declaration of new variables at the top of the
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current scope. This allows assignment to be used as a piece of an
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expression.
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</p>
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<%= code_for('expressions_assignment', 'six') %>
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<p id="aliases">
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<b class="header">Aliases</b>
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Because the <tt>==</tt> operator frequently causes undesirable coercion,
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is intransitive, and has a different meaning than in other languages,
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CoffeeScript compiles <tt>==</tt> into <tt>===</tt>, and <tt>!=</tt> into
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<tt>!==</tt>.
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In addition, <tt>is</tt> compiles into <tt>===</tt>,
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and <tt>isnt</tt> into <tt>!==</tt>.
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</p>
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<p>
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You can use <tt>not</tt> as an alias for <tt>!</tt>.
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</p>
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<p>
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For logic, <tt>and</tt> compiles to <tt>&&</tt>, and <tt>or</tt>
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into <tt>||</tt>.
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</p>
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<p>
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Instead of a newline or semicolon, <tt>then</tt> can be used to separate
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conditions from expressions, in <b>while</b>,
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<b>if</b>/<b>else</b>, and <b>switch</b>/<b>when</b> statements.
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</p>
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<p>
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As in <a href="http://yaml.org/">YAML</a>, <tt>on</tt> and <tt>yes</tt>
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are the same as boolean <tt>true</tt>, while <tt>off</tt> and <tt>no</tt> are boolean <tt>false</tt>.
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</p>
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<p>
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For single-line statements, <tt>unless</tt> can be used as the inverse of <tt>if</tt>.
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</p>
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<%= code_for('aliases') %>
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<p id="while">
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<b class="header">While Loops</b>
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The only low-level loop that CoffeeScript provides is the while loop.
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</p>
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<%= code_for('while') %>
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<p>
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Other JavaScript loops, such as <b>for</b> loops and <b>do-while</b> loops
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can be mimicked by variations on <b>while</b>, but the hope is that you
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won't need to do that with CoffeeScript, either because you're using
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<b>each</b> (<b>forEach</b>) style iterators, or...
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</p>
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<p id="array_comprehensions">
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<b class="header">Array Comprehensions</b>
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For your looping needs, CoffeeScript provides array comprehensions
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similar to Python's. They replace (and compile into) <b>for</b> loops, with
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optional guard clauses and the value of the current array index.
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Unlike for loops, array comprehensions are expressions, and can be returned
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and assigned. They should be able to handle most places where you otherwise
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would use a loop, <b>each</b>/<b>forEach</b>, <b>map</b>, or <b>select</b>/<b>filter</b>.
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</p>
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<%= code_for('array_comprehensions') %>
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<p id="slice">
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<b class="header">Slicing Arrays with Ranges</b>
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CoffeeScript borrows Ruby's
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<a href="http://ruby-doc.org/core/classes/Range.html">range syntax</a>
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for extracting slices of arrays. With two dots (<tt>3..5</tt>), the range
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is inclusive: the first argument is the index of the first element in
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the slice, and the second is the index of the last one. Three dots signify
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a range that excludes the end.
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</p>
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<%= code_for('slices', 'numbers_copy') %>
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<p id="inheritance">
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<b class="header">Inheritance, and Calling Super from a Subclass</b>
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JavaScript's prototypal inheritance has always been a bit of a
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brain-bender, with a whole family tree of libraries that provide a cleaner
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syntax for classical inheritance on top of JavaScript's prototypes:
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<a href="http://code.google.com/p/base2/">Base2</a>,
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<a href="http://prototypejs.org/">Prototype.js</a>,
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<a href="http://jsclass.jcoglan.com/">JS.Class</a>, etc.
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The libraries provide syntactic sugar, but the built-in inheritance would
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be completely usable if it weren't for a couple of small exceptions:
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it's awkward to call <b>super</b> (the prototype object's
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implementation of the current function), and it's awkward to correctly
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set the prototype chain. CoffeeScript provides <tt>extends</tt>
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to help with prototype setup, and converts
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<tt>super()</tt> calls into calls against the immediate ancestor's
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method of the same name.
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</p>
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<%= code_for('super', true) %>
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<p id="embedded">
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<b class="header">Embedded JavaScript</b>
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If you ever need to interpolate literal JavaScript snippets, you can
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use backticks to pass JavaScript straight through.
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</p>
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<%= code_for('embedded', 'hi()') %>
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<p id="switch">
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<b class="header">Switch/When/Else</b>
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<b>Switch</b> statements in JavaScript are rather broken. You can only
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do comparisons based on string equality, and need to remember to <b>break</b> at the end of
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every <b>case</b> statement to avoid accidentally falling through to
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the default case. CoffeeScript compiles <b>switch</b> statements into JavaScript if-else chains, allowing you to
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compare any object (via <b>===</b>), preventing fall-through, and resulting
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in a returnable, assignable expression. The format is: <tt>switch</tt> condition,
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<tt>when</tt> clauses, <tt>else</tt> the default case.
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</p>
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<%= code_for('switch') %>
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<p id="try">
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<b class="header">Try/Catch/Finally</b>
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Try/catch statements are just about the same as JavaScript (although
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they work as expressions).
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</p>
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<%= code_for('try') %>
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<p id="try">
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<b class="header">Multiline Strings</b>
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Multiline strings are allowed in CoffeeScript.
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</p>
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<%= code_for('strings', 'moby_dick') %>
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<h2 id="contributing">Contributing</h2>
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<p>
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Here's a wish list of things that would be wonderful to have in
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CoffeeScript:
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</p>
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<ul>
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<li>
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A JavaScript version of the compiler, perhaps using Alessandro Warth's
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<a href="http://tinlizzie.org/ometa/">OMeta</a>.
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</li>
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<li>
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Ideas for alternate syntax to end blocks of expressions — the periods
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can look a little weird with deeply nested structure.
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</li>
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<li>
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Test cases for any syntax errors you encounter that you think CoffeeScript
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should be able to compile properly.
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</li>
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<li>
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A tutorial that introduces CoffeeScript from the ground up for folks
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without knowledge of JavaScript.
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</li>
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<li>
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Integration with Processing.js's JavaScript API (this would depend on
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having a JavaScript version of the compiler).
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</li>
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<li>
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A lot of the code generation in <tt>nodes.rb</tt> gets into messy
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string manipulation. Techniques for cleaning this up across the board
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would be appreciated.
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|
</li>
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</ul>
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|
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|
<h2 id="change_log">Change Log</h2>
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|
|
|
<p>
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<b class="header" style="margin-top: 20px;">0.1.4</b>
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The official CoffeeScript extension is now <tt>.coffee</tt> instead of
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|
<tt>.cs</tt>, which properly belongs to
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|
<a href="http://en.wikipedia.org/wiki/C_Sharp_(programming_language)">C#</a>.
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|
Due to popular demand, you can now also use <tt>=</tt> to assign. Unlike
|
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JavaScript, <tt>=</tt> can also be used within object literals, interchangeably
|
|
with <tt>:</tt>. Made a grammatical fix for chained function calls
|
|
like <tt>func(1)(2)(3)(4)</tt>. Inheritance and super no longer use
|
|
<tt>__proto__</tt>, so they should be IE-compatible now.
|
|
</p>
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|
|
|
<p>
|
|
<b class="header" style="margin-top: 20px;">0.1.3</b>
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|
The <tt>coffee</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>
|
|
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</body>
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</html>
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