2. About Me
Mike Edwards
M.S. Computer Science, University of Iowa
Started building web applications professionally in 2000
JavaScript expert level
jQuery: Started using it about 1.5 years ago
Used extensively since then
I'm very interested in common themes across different
technologies
3. Outline
● Introduction
○ UserScripts: Greasemonkey, Tampermonkey
○ Filtering Script: Demo, Code Review
● Thinking about Perspective
○ Looking at the same thing from a different angle
○ The Perspective of Source Control
○ Filtering Script: From a New Perspective
● A Basic MVC Plugin Architecture
○ Modular Architecture
○ Refactoring: Quick Intro
○ jQuery & MVC
○ Plugin Ecosystems
○ Filtering: Refactored
4. User Scripts
● Supporting Add-ons:
○ Greasemonkey, Tampermonkey
● Scripts are installed by the user in their
browser, not by a web admin on the server
● User scripts make on-the-fly changes to a
web page's content as the page is loaded
into the users browser
● As long as the script doesn't use any of it's
escalated privileges, it can be loaded directly
onto the server for all users
10. Perspective: Computability
● This concept runs right to the bedrock of all
Computer Science
● Church/Turing Thesis
○ Lambda Calculus and Turing Machines are
equivalent ways of looking at computability
● Electrical Engineering: You can build an
entire CPU out of just NAND logic gates.
You can also build it out of just NOR logic
gates.
13. Merge or Modularize
● jQuery "Feature Files" consist of "payload" code and
"merge instructions" about where to splice in the
payloads
● One approach once we've successfully prototyped a new
feature is to then manually merge it into the application
code-base (Feature Branching/Merge)
● Feature Branching is a poor man's modular architecture, instead of
building systems with the ability to easy swap in and out features at
runtime / deploytime they couple themselves to the source control
providing this mechanism through manual merging.
-- Dan Bodart
http://martinfowler.com/bliki/FeatureBranch.html
14. Technical Debt & Refactoring
● Technical Debt:
"You have a piece of functionality that you need to add to your system.
You see two ways to do it, one is quick to do but is messy - you are sure
that it will make further changes harder in the future. The other results in a
cleaner design, but will take longer to put in place."
- Martin Fowler
● Refactoring:
"a disciplined technique for restructuring an existing body of code,
altering its internal structure without changing its external behavior"
- Wikipedia
15. Plugin Ecosystems
● Users can decide for themselves via
configuration which features they need
● Third-party developers can potentially
enhance the value of your product at no cost
to you
● An API built for plugins can be used for
integration with partner applications and/or
used as a backend for additional platforms
(mobile web, mobile native)
21. jQuery & MVC cont.
● Most "MVC" frameworks focus on "MV"
○ Observable models
○ Template based rendering
○ Data Binding/Automatic re-rendering
● jQuery specializes in "C" with a side of "V"
○ Event Handlers
○ AJAX
○ Powerful ability to update the View in real-time, but
no template support or observable models
28. Refactoring Continued...
● Pitfall: Because jQuery is so good at
Querying the view, it can be tempting to
simply treat the view as your model.
● This is okay for prototypes and tiny features,
but should be refactored when possible
● We've re-organized the code by it's MVC
role, which is a start
● Still need to flesh-out and integrate with the
underlying application infrastructure
29. Branch/Merge vs Plugins
Version Control Plugin Architecture
Trunk Application Core Architecture
Branch Start New Plugin
Merge/Patch Load Plugin at Run-time
Cherry-picking Enable/Disable Plugins
30. Conclusion
● jQueries power comes, at least partly, from
it's ability to weave "merge" code inline
● An alternate way to view this is that jQuery
provides the infrastructure necessary to
create Application level plugins
● Aspect-Oriented Programming as an entire
field dedicated to this kind of thinking
