Johnson at RubyConf 2008

“O Muses, O high genius, aid me now!
O memory that engraved the things I saw,
Here shall your worth be manifest to all!”
Dante Alighieri
Saturday, November 8, 2008

Introductions and
Expense Reports

John Barnette
jbarnette@rubyforge.org
github.com/jbarnette
twitter.com/jbarnette

Aaron
Patterson
aaronp@rubyforge.org
tenderlovemaking.com
github.com/tenderlove
twitter.com/tenderlove
猫舌です

(they totally paid)

A Tale of Two Languages

JavaScript
• Mocha! No, LiveScript! No! JAVASCRIPT!
• Brendan Eich’s fault
• Schemey, with Self’s prototypes and C’s
syntax
• But not really

JavaScript objects are bags of slots.
obj = {}
obj["hello"] = "world"
obj.hello == obj["hello"]
// => true

JavaScript functions are ﬁrst-class.
hello = function(name) {
return "Hello, " + name + "!"
}
hello("internets")
// => "Hello, internets!"

...but they can ‘belong’ to an object
aaron = { name: "Aaron" }
aaron.hello = function() {
return "Hello, " + this.name + "!"
}
aaron.hello()
// => "Hello, Aaron!"

JavaScript doesn’t have classes.
function Greeter(name) {
this.name = name
}
Greeter.prototype.hello = function() {
return "Hello, " + this.name + "!"
}
aaron = new Greeter("Aaron")
aaron.hello()
// => "Hello, Aaron!"

Whatever.
Why do I care?

Because it’s freaking
EVERYWHERE.

There’s JavaScript Here!
(this may be a lie)

Ruby
• Invented in 1650 by Baruch Spinoza
• Mostly used to program industrial looms
• Half the sodium of the leading brand
• (this may be a lie)

INTERNETS.

WORLD WIDE
WEBTERNETS.

Client / Server
JavaScript / Ruby
Prototype / Rails
jQuery / Merb

“Two houses, both alike
in dignity...”

For JavaScript, the
browser IS the runtime.

Tight Coupling
Do the
dishes
But I
want to
watch TV

Sweet STDLIB
• Modify DOM trees

Excellent Code
Packagers
•

Great CLI Test
Frameworks
•

Continuous Integration
Systems
•
• (just hit refresh)

EVERYTHING
depends on
THE BROWSER

lame.

Free the runtime!
• Browserless testing
• Access to the ﬁlesystem
• Easy extension
• Easy experimentation (where’s my IRB?)

Johnson

(this is not a juvenile
penis joke)

(that’s what she said)

Johnson bridges the
Great Divide.

Use JavaScript in your Ruby!
doubler = Johnson.evaluate <<-END
function(x) { return x * 2 }
END
[1, 2, 3].collect(&doubler)
# => [2, 4, 6]

Use Ruby in your JavaScript!
Ruby.require("open-uri")
function hasObamaWonYet() {
var page = Ruby.open(
"http://hasobamawonyet.com").read()
return page.match(/YES/)
}
Ruby.puts(hasObamaWonYet())
// => YES

you just blew my mind.

I love
you, Ruby!
Whatever.
Hold still.

The Dynamic Internets

AJAX
• Aaron’s
• JavaScript
• Aaron
• eXchange

screen scraping isn’t
just for douchebags

Innernets

What Do We Do?

Mechanize

<html>
<body>
<p id='testing'>Hello world</p>
<script>
var p_tag = document.getElementById('testing');
p_tag.firstChild.textContent = 'Welcome to IHON!';
</script>
</body>
</html>
Client Side JavaScript

It’s Wrong!
agent = WWW::Mechanize.new
page = agent.get('http://localhost/~aaron/some_html.html')
puts page.search('p').first.text # => Hello world

But with Johnson....
agent = WWW::Mechanize.new
page = agent.get('http://localhost/~aaron/some_html.html')
puts page.search('p').first.text # => Welcome to IHON

Using the Johnson Shell

js> alert('hello world!')
alert is not defined at ((console)):1
@(console):1
js> rb
rb> js['alert'] = lambda { |msg| puts msg }
=> #<Proc:0x00475d24@bin/johnson:13>
rb> js
js> alert('hello world')
hello world
=> nil

js> var iterator = function(x) { return x * x }
=> nil
js> rb
rb> js_iterator = js['iterator']
=> function (x) {
return x * x;
}
rb> [1,2,3,4].map(&js_iterator)
=> [1, 4, 9, 16]

Johnson Proxies

Everything is an Object

Ruby
Object
JavaScript
Object
こんにちは
Hello!

+9 Cloak of Invisibility

Ruby Country JavaScript Country
You must have
a cape before
crossing!
JavaScript
Object
Ruby
Object

Ruby Country
Ruby
Object
こんにちは
JavaScript
Object
こんにちは

JavaScript Country
Hello!
JavaScript
Object
Hello!
Ruby
Object

rb> some_object= Object.new
=> #<Object:0x477034>
rb> js[:cloaked_object] = some_object
=> #<Object:0x477034>
rb> js
js> cloaked_object.foo = "hello!"
=> "hello!"
js> cloaked_object.bar = function(x) { return x * 3 }
=> function (x) {
return x * 3;
}
js> rb
rb> some_object.foo
=> "hello!"
rb> some_object.bar(10)
=> 30

Fancy Marshalling
rb> js[:matcher] = /internets/
=> /internets/
rb> js
js> matcher.constructor
=> function RegExp() {
[native code]
}
js> "internets!".match(matcher)
=> internets

Attaching JS Functions
rb> blank = Object.new
=> #<Object:0x466bf8>
rb> js[:blank] = blank
=> #<Object:0x466bf8>
rb> js
js> blank.awesome = function()
{ return "Awesome!" }
=> function () {
return "Awesome!";
}
js> rb
rb> blank.awesome
=> "Awesome!"

Attaching JS Functions EVERYWHERE
js> Ruby.String.prototype.embiggen =
function() { return this.toUpperCase() }
=> function () {
return this.toUpperCase();
}
js> rb
rb> "this is pure evil.".embiggen
=> "THIS IS PURE EVIL."

Things that are Hard

Garbage Collection

Threading

I’m Not Convinced

Johnson Sounds Dumb
• You are wrong.

Case In Point

def fib n
return n if [0, 1].include?(n)
fib(n - 1) + fib(n - 2)
end

rt = Johnson::Runtime.new
rt.evaluate(<<-eojs)
var fib = function(n) {
if(n == 0) return n;
return fib(n - 1) + fib(n - 2);
}
eojs

class TellA
def initialize
@rt = Johnson::Runtime.new
@rt.evaluate(<<-eojs)
var fib = function(n) {
return fib(n - 1) + fib(n - 2);
}
eojs
end
def fib n
return n if [0, 1].include?(n)
fib(n - 1) + fib(n - 2)
end
def second_fib n
@rt['fib'].call(n)
end
end

class TestFib < Test::Unit::TestCase
def test_awesomeness
@tell_a = TellA.new
assert_equal @tell_a.fib(30), @tell_a.second_fib(30)
end
end

Which One is Faster?

We’re helpful!
(things you’ll probably need)

Loading JS Files
// search Ruby's load path
Johnson.require("myjs")

Gettin’ at Ruby Stuff
// everything's available!
hash = new Ruby.Hash()
// ...including kernel methods
Ruby.puts("I made a hash!")
// ...and nested stuff
mine = new Ruby.Thing.In.Namespace()

Symbology
// we keep a cache of symbols
sym = Johnson.symbolize("monkey")
// ...and mix in to String.prototype
sym = "monkey".toSymbol()

Where am I?
where = __FILE__
=> "cheese.js"

Johnson
(the not so practical)

Database Access

[aaron@Jordan ar_js]$ ../johnson/bin/johnson
js> rb
rb> require 'config/environment'
=> true
rb> require 'user'
=> ["User"]
rb> js
js> var users = Ruby.User.find(Johnson.symbolize("all"))
=> nil
js> users.each(function(user) { Ruby.puts(user.name()) });
Aaron Patterson
John Barnette
=> [#<User id: 1, name: "Aaron Patterson", occupation:
"internetexpert", created_at: "2008-11-05 19:14:04",
updated_at: "2008-11-05 19:14:04">, #<User id: 2, name:
"John Barnette", occupation: "webinarchitect", created_at:
"2008-11-05 19:14:04", updated_at: "2008-11-05 19:14:04">]
js>

EJS

RailsViews in JS
class UsersController < ApplicationController
def index
@users = User.find(:all)
end
end
Traditional Ruby Controller

RailsView in JS
EJS File (app/views/index.html.ejs)
<html>
<body>
<h1>こんにちは！</h1>
<ul>
<% for(var user in at.users) { %>
<li><%= user.name() %></li>
<% } %>
</ul>
</body>
</html>

Rails Plugin Available
with Johnson
johnson/lib/rails/init.rb

Breakpoints
break it down

require 'johnson'
runtime = Johnson::Runtime.new
# Compile our script
script = runtime.compile('var x = 0;
for(var i = 0; i < 10; i++) {
x += 2; // Line 3
}', "my_script")
# Set the breakpoint
runtime.break('my_script', 3) do
puts "i = #{runtime['i']}, x = #{runtime['x']}"
end
# Evaluate the compiled script
runtime.evaluate_compiled_script(script)

[aaron@Jordan demos]$ ruby breakpoints.rb
i = 0, x = 0
i = 1, x = 2
i = 2, x = 4
i = 3, x = 6
i = 4, x = 8
i = 5, x = 10
i = 6, x = 12
i = 7, x = 14
i = 8, x = 16
i = 9, x = 18
[aaron@Jordan demos]$

HotRuby.js

The Ruby Code
puts “Hello World”

The Byte Code
"["YARVInstructionSequence/SimpleDataFormat
",1,1,1,{"arg_size":0,"local_size":
1,"stack_max":2},"<compiled>","src","top
",[],0,[],[1,["trace",1],["putnil"],
["putstring","Hello World"],["send","puts
",1,null,8,null],["leave"]]]"
Yuck!

[aaron@Jordan rubyconf (master)]$ ~/git/
johnson/bin/johnson
js> Johnson.require('HotRuby')
=> true
js> var hr = new HotRuby();
=> nil
js> hr.run(eval("(" +
"["YARVInstructionSequence/SimpleDataFormat
",1,1,1,{"arg_size":0,"local_size":
1,"stack_max":2},"<compiled>","src","top
",[],0,[],[1,["trace",1],["putnil"],
["putstring","Hello World"],["send",
"puts",1,null,8,null],["leave"]]]" + ")"));
Hello World
=> nil
js> exit

Ruby

on JavaScript

on Ruby

on Rails
just kidding (or am I?)

One More Thing

JS Parse Tree

tree = Johnson::Parser.parse(<<-eojs)
var foo = function(x) {
return x * 10;
}
foo.call(10);
eojs

AST Provides
• Directed Graph Representation (DOT)
• SEXP For easy reading
• #each for easy manipulation
• #to_js for easy generation

tree.each do |node|
case node
when Johnson::Nodes::Name
node.value = 'hello' if node.value == 'foo'
end
end
puts tree.to_js
Given the Earlier Tree

Parse This!
rt = Johnson::Runtime.new
rt.evaluate(<<-eoecma)
// Parse the javascript
var tree = Ruby.Johnson.Parser.parse("alert('hello world')");
// Change alert to Ruby.puts
tree.each(function(node) {
if(node.value == 'alert') {
node.value = 'Ruby.puts';
}
});
// Eval the result
eval(tree.to_js());
eoecma

So.
• 1.0 is good to go
• Ruby 1.8.6, unixish and Windows
• Stability? Okay.

Thanks!
• Yehuda Katz
• Matthew Draper
• John Resig

github.com/jbarnette/johnson

Johnson at RubyConf 2008

Recommended

Recommended

More Related Content

Similar to Johnson at RubyConf 2008

Similar to Johnson at RubyConf 2008 (20)

Recently uploaded

Recently uploaded (20)

Johnson at RubyConf 2008