Slide 1
Slide 1 text
Reusing your frontend JS
on the server with V8/Rhino
Pushing SRP & DI/IoC to whole new level
Slide 2
Slide 2 text
Kenneth Kalmer
Chief Rocket Scientist @ ValuationUP.com
@kennethkalmer
github/kennethkalmer
www.opensourcery.co.za
kennethkalmer
Slide 3
Slide 3 text
ValuationUP.com
Help entrepreneurs make REAL sense of their
management accounts
Comparative analysis within industry
Refactoring financials by getting from red to green
Take actions to increase their valuations
Valuation is the ultimate metric
Slide 4
Slide 4 text
The challenge
We need a very responsive UI
Realtime updates as the user inputs information
The RTT to the server is not worth the wait for such a
simple formula
Slide 5
Slide 5 text
No content
Slide 6
Slide 6 text
Done!
Repeat that for 50+ financial models
Build fully buzzword compliant frontend
Slide 7
Slide 7 text
Panic!
Let’s offer a PDF with all the information
A PDF...
...WITH ALL THE INFORMATION
Slide 8
Slide 8 text
No content
Slide 9
Slide 9 text
We did it!
But how?
Slide 10
Slide 10 text
Dilemma
Duplicate?
Reuse?
wkhtmltopdf? (a.k.a. wtftopdf)
Slide 11
Slide 11 text
Reuse!
Single Responsibility Principle
Dependency Injection/Inversion on Control
Use as much JS on the server as possible, where
possible!
Slide 12
Slide 12 text
By using
therubyracer (github.com/cowboyd/rubyracer)
therubyrhino (github.com/cowboyd/rubyrhino)
coffee-script
1 gem 'therubyracer', platforms: :ruby
2 gem 'therubyrhino', platforms: :jruby
3
4 gem 'coffee-script'
Slide 13
Slide 13 text
That’s WACC!
Slide 14
Slide 14 text
With coffee
1 # Determine the WACC of the business (weighted average cost of capital)
2 class Demo.WACC
3
4 constructor: (statement) ->
5 @statement = statement
6
7 @cost_of_equity = statement.cost_of_equity
8 unless _.isFinite( @cost_of_equity )
9 @cost_of_equity = 0.30
10
11 calculate: ->
12
13 e = ( @statement.equity / ( @statement.debt + @statement.equity ) ) * @cost_of_equity
14 d = ( @statement.debt / ( @statement.debt + @statement.equity ) ) * @statement.costOfDebt
15 t = ( 1 - @statement.taxRate )
16
17 e + d * t
18
19 # Return the calculated WACC
20 value: ->
21 @wacc or= @calculate()
Slide 15
Slide 15 text
Present it
1 class Demo.WaccLayout
2
3 # The view that will render our information
4 view: null
5
6 initialize: (data, view = null) ->
7 @data = data
8 @view = view
9
10 render: ->
11 wacc = new Demo.WACC( @data.statement )
12
13 @view.render( wacc: wacc.value() )
Slide 16
Slide 16 text
Client-side view & usage
1 # Simple backbone view
2 class Demo.WaccView extends Backbone.View
3
4 render: (options) ->
5 wacc = options.wacc
6
7 @$el.empty().append( "
#{wacc}
" ) 8 9 10 11 12 13 # Initialize a view 14 view = new Demo.WaccView( el: '#wacc' ) 15 16 # Load and render our layout 17 layout = new Demo.WaccLayout( view: view, data: data ) 18 layout.render()Slide 17
Slide 17 text
Reuse on the server...
Slide 18
Slide 18 text
JavaScript Context
1 require 'v8'
2 # require 'rhino'
3
4 # This service wraps a JS context and allows us to interact with our Javascript
5 # directly in Ruby.
6 class Javascript
7
8 # Our V8 context object
9 attr_reader :context
10
11 # Some delegations
12 delegate :load, :eval, :[], :[]=, to: :context
13
14 def initialize()
15 @context = V8::Context.new
16 #@context = Rhino::Context.new
17
18 # Setup a fake 'window' object
19 @context['window'] = FakeWindow.new( @context )
20 @context['console'] = FakeConsole.new
21
22 # Load our global setup
23 load_coffee Rails.root.join( 'app/assets/javascripts/setup.js.coffee' )
24 end
25
26 # truncated, lots more detracting stuff down below...
27
28 end
Slide 19
Slide 19 text
CoffeeScript sprinkles
1 # Compile and load a CoffeeScript file into the current context
2 def load_coffee( path )
3 compiled_coffeescript = CoffeeScript.compile( File.read( path ) )
4 context.eval compiled_coffeescript
5 end
Slide 20
Slide 20 text
Pause
We have a JavaScript context (V8) at our finger tips
Have some basic CoffeeScript loading abilities
And some additional plumbing
Far from a DOM
Slide 21
Slide 21 text
Server-side wrapper
1 class WaccLayout
2
3 def initialize( view, context = Javascript.new )
4 @context = context
5
6 load_dependencies
7
8 # Pass our Ruby view into the context
9 @context["view"] = view
10
11 # Setup
12 @context.eval <<-EOJS
13 var layout = new Demo.WaccLayout({
14 view: view, data: data
15 });
16 EOJS
17 end
18
19 def render
20 context['layout']['render'].methodcall( context['layout'] )
21 end
22
23 def load_dependencies
24 @context.load_coffee Rails.root.join("app/assets/javascripts/wacc.js.coffee")
25 @context.load_coffee Rails.root.join("app/assets/javascripts/wacc_layout.js.coffee")
26 end
27 end
Slide 22
Slide 22 text
Server-side view & usage
1 class WaccPdf
2
3 def initialize
4 @pdf = Prawn::Document.new
5 end
6
7 def render( options )
8 wacc = options.wacc
9
10 @pdf.text "WACC: #{wacc}"
11 end
12
13 end
14
15
16 # Setup a view
17 view = WaccPdf.new
18
19 # Setup a layout and render
20 layout = WaccLayout.new( view )
21 layout.render
Slide 23
Slide 23 text
1,000 ft view
Slide 24
Slide 24 text
Reminder why we did it?
Slide 25
Slide 25 text
No content
Slide 26
Slide 26 text
Yes please!
https://github.com/kennethkalmer/rubyfuza-2013
https://rubyfuza-2013-wacc.herokuapp.com
Later this weekend, you’re all getting drunk tonight
anyway!!
Slide 27
Slide 27 text
Thank you!
It’s been wild!