asciidoctor.js

= asciidoctor.js, AsciiDoc in JavaScript Dan Allen :idprefix: :idseparator: - :sources: https://github.com/asciidoctor/asciidoctor.js :license: https://github.com/asciidoctor/asciidoctor.js/blob/master/LICENSE

This project uses http://opalrb.org[Opal] to cross-compile http://asciidoctor.org[Asciidoctor], an implementation of AsciiDoc, from Ruby to JavaScript to produce asciidoctor.js, which brings http://asciidoc.org[AsciiDoc] to the browser!

== Introduction

The {sources}[asciidoctor.js project] is direct port of http://asciidoctor.org[Asciidoctor] from Ruby to JavaScript using the http://opalrb.org[Opal] Ruby-to-JavaScript cross compiler. It consists of a Rake build script that executes the Opal compiler on the Asciidoctor source code to produce the asciidoctor.js script.

Opal parses the Ruby code and any required libraries, then rewrites the code into JavaScript under the Opal namespace. The resulting JavaScript can be executed within any JavaScript runtime environment (such as a browser).

To interact with the generated code, you either invoke the JavaScript APIs directly, or you can invoke native JavaScript objects from within the Ruby code prior to compilation.

== Setup

To build asciidoctor.js, you need some tools :

• Npm and Node
• Bower
• Rake and Bundle

Start by cloning the source from GitHub:

$ git clone git://github.com/asciidoctor/asciidoctor.js

Next, switch to the 'asciidoctor.js' directory and run Npm's +install+ command and Bower's +install+ command:

$ cd asciidoctor.js $ npm install $ bower install

You're now ready to build asciidoctor.js.

[TIP]

Opal.js, The Ruby runtime in JavaScript is available in +bower_components/opal/opal/current/opal.min.js+

== Building asciidoctor.js

To build asciidoctor.js, simple run the Grunt +dist+ task from the root of the project:

$ grunt dist

NOTE: The build task will make some minor code changes on the asciidoctor submodule. As you may know String are immutable in Javascript, so we need to replace +gsub!+ and +sub!+ methods. These changes are made at build time to keep the Ruby code as fast as possible.

This command produces some files in the 'dist' directory:

• dist/

• asciidoctor.js (includes core and extensions)
• asciidoctor-core.js (no extensions API)
• asciidoctor-extensions.js (extensions API only)
• asciidoctor-all.js (core, extension and Opal)

• dist/npm (to use with Npm)

• asciidoctor-core.js (no extensions API)
• asciidoctor-extensions.js (extensions API only)

Each file has a +minified+ and +gz+ version.

You'll see these scripts in action when you run the examples, described next.

== Building and running the examples

To build the examples, simply run the Rake +examples+ task from the root of the project:

$ grunt examples

This command produces another JavaScript file in the 'build' directory, 'asciidoctor_example.js'. This script includes:

• a string that contains an AsciiDoc source document
• a call to the Asciidoctor API to render the content of that string to HTML
• an event listener that inserts the generated HTML into the page

All the JavaScript in that file was generated from a Ruby script by Opal.

Point your browser at 'build/asciidoctor_example.html'. You should see the AsciiDoc Syntax Quick Reference document. The content on the page was rendered from AsciiDoc by asciidoctor.js when you loaded the page!

== Using Asciidoctor in JavaScript

There are two ways to use the JavaScript version of Asciidoctor:

. Write code in Ruby that hooks into the native JavaScript environment, which Opal compiles into JavaScript . Invoke the JavaScript APIs that Opal generates directly from JavaScript

=== Using Asciidoctor and the native JavaScript environment from Ruby

First, we'll stuff some AsciiDoc data into a variable inside a Ruby script:

[source,ruby]

data = <<-EOS = asciidoctor.js, AsciiDoc in JavaScript Doc Writer [e-mail]

Asciidoctor and Opal come together to bring http://asciidoc.org[AsciiDoc] to the browser!.

== Technologies

• AsciiDoc
• Asciidoctor
• Opal

NOTE: That's all she wrote! EOS

Next, we invoke Asciidoctor in Ruby just as we normally would:

[source,ruby]

html_doc = Asciidoctor.render(data, :safe => :safe, :attributes => %w(notitle! anchors imagesdir=./images))

We then use the global +$window+ object provided by Opal to register a listener that inserts the rendered HTML document into the page:

[source,ruby]

$window.addEventListener 'DOMContentLoaded', proc { $document.getElementById('content').innerHTML = html_doc }, false

The final step is to compile this Ruby code into JavaScript using the Opal compiler.

[source,ruby]

env = Opal::Environment.new env.append_path 'examples' compiled = env['asciidoctor_example'].to_s File.open('build/asciidoctor_example.js', 'w') { |f| f << compiled }

When the 'asciidoctor_example.js' script is loaded by the browser, the Ruby code (compiled as JavaScript) is executed, rendering the AsciiDoc document and inserting the result into the page.

You can also invoke Asciidoctor directly from JavaScript.

== Using Asciidoctor from JavaScript

If you choose, you may use the Asciidoctor class that Opal generates directly from Ruby.

=== Front-end development

Asciidoctor.js gives you its files using http://bower.io[Bower].

Start by install asciidoctor.js component : [source, shell]

bower install asciidoctor.js --save

NOTE: Asciidoctor.js has a dependency with opal and when you run the install command, Opal is automatically downloaded in +bower_components/opal/+

You need to load file(s) into your JavaScript environment to use Asciidoctor. For instance, in an HTML page, add these +

[source,html]

---

If you don't want to use extensions, you can load files separately :

[source,html]

---

All Opal-compiled classes are stored under the Opal namespace. Ruby variables and methods on a class or object get prefixed with +$+. Thus, where you would execute +Asciidoctor.convert+ in Ruby, you execute +Opal.Asciidoctor.$convert+ in JavaScript.

[source,javascript]

var html_doc =Opal.Asciidoctor.$convert( "http://asciidoctor.org[*Asciidoctor*] " + "running on http://opalrb.org[_Opal_] " + "brings AsciiDoc to the browser!")

You would insert the rendered document into the page using the normal JavaScript DOM methods:

[source,javascript]

document.getElementById('content').innerHTML = Opal.Asciidoctor.$convert( "http://asciidoctor.org[*Asciidoctor*] " + "running on http://opalrb.org[_Opal_] " + "brings AsciiDoc to the browser!")

Passing the options +Hash+ to the +convert+ method requires a little bit of Opal voodoo:

[source,javascript]

Opal.hash2(['attributes'], {'attributes': ['notitle!']})

=== Back-end development

For back-end development, we use npm.

Start by install asciidoctor.js module:

[source, javascript]

npm install asciidoctor.js --save

You need to load file into your application. For instance, in a Javascript file, add these line : [source, javascript]

var asciidoctorObject = require('asciidoctor.js')();

// You can get Opal var opal = asciidoctorObject.Opal;

// You can get Asciidoctor with Extensions ... var asciidoctorWithExtensions = asciidoctorObject.Asciidoctor(true); // ... or without extensions var asciidoctorWithoutExtensions = asciidoctorObject.Asciidoctor();

// Now you can use it var html = Asciidoctor.$convert('== Test', opal.hash2(['attributes'], {'attributes': ['notitle!']}));

// And for example log it console.log(html);

/* // Should return

Test

*/ ----

== Changes to Asciidoctor (from upstream)

Compiling Asciidoctor to JavaScript currently requires some changes in Asciidoctor. That's why the Asciidoctor source is linked into the project as a Git submodule. The goal is to eventually eliminate all of these differences so that Asciidoctor can be compiled to JavaScript as is.

Here's a list of some of the changes that are currently needed:

• Named posix groups in regular expressions are replaced with their ASCII equivalent

  • JavaScript doesn't support named posix groups, such as +[[:alpha:]]+)

• A shim library is needed to implement missing classes in Opal, such as +Set+, +File+ and +Dir+

• All mutable String operations have been replaced with assignments

  • JavaScript doesn't support mutable strings

• $~[0] used in place of $& and $~[n] in place of $n after running a regular expression (where n is 1, 2, 3...)

• +Set+ is missing difference and union operations

• Opal doesn't recognize modifiers on a regular expression (e.g., multiline)

• Optional, non-matching capture groups resolve to empty string in gsub block in Firefox (see http://www.bennadel.com/blog/1916-different-browsers-use-different-non-matching-captured-regex-pattern-values.htm)

• Assignments without a matching value are set to empty string instead of nil (in the following example, +b+ is set to empty string)

  a, b = "value".split ',', 2

• ...

== Debugging

Compiling a Ruby application to JavaScript and getting it to run is a process of eliminating fatal errors. When the JavaScript fails, the message isn't always clear or even close to where things went wrong. The key to working through these failures is to use the browser's JavaScript console.

=== Chrome / Chromium

Chrome (and Chromium) has a very intuitive JavaScript console. To open it, press kbd:[Ctrl+Shift+J] or right-click on the page, select "Inspect Element" from the context menu and click the "Console" tab.

When an error occurs in the JavaScript, Chrome will print the error message to the console. The error message is interactive. Click on the arrow at the start of the line to expand the call trace, as shown here:

image::error-in-chrome-console.png[]

When you identify the entry you want to inspect, click the link to the source location. If you want to inspect the state, add a breakpoint and refresh the page.

Chrome tends to cache the JavaScript files too aggressively when running local scripts. Make a habit of holding down kbd:[Ctrl] when you click refresh to force Chrome to reload the JavaScript.

Another option is to start Chrome with the application cache disabled.

$ chrome --disable-application-cache

=== Firefox

Firefox also has a JavaScript console. To open it, press kbd:[Ctrl+Shift+J] or right-click on the page, select "Inspect Element" from the context menu and click the "Web Console" tab.

When an error occurs in the JavaScript, Firefox will print the error message to the console. Unlike Chrome, the error message is not interactive. Its power, instead, lies under the hood.

To see the call trace when an exception occurs, you need to configure the Debugger to pause on an exception. Click the "Debugger" tab, click the configuration gear icon in the upper right corner of that tab and click "Pause on exceptions". Refresh the page and you'll notice that the debugger has paused at the location in the source where the exception is thrown.

image::error-in-javascript-debugger.png[]

The call trace is displayed as breadcrumb navigation, which you can use to jump through the stack. You can inspect the state at any location by looking through the panels on the right.

== Copyright

Copyright (C) 2013 Dan Allen. Free use of this software is granted under the terms of the MIT License.

See the {license}[LICENSE] file for details.