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Detangling Your JavaScript An Intro to JS Refactoring
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Chris Powers Engineering Manager at Groupon @chrisjpowers
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A Conversation
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“Are you using JavaScript or jQuery?”
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What is “Tangled” JavaScript?
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It is not BROKEN code!
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Broken code doesn’t work.
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Tangled code does work, but...
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Tangled code will become “broken” code eventually because...
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Tangled code is hard to read and understand.
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Tangled code is hard to update and maintain.
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Tangled code is easy to accidentally break.
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“Tangled code is code based on lost requirements.” - Noel Rappin
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Tangled code was shaped by forces that YOU aren’t aware of
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Got Tangled Code? Do you...
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Option #1: Big Bang Rewrite
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Option #2: Detangle (Refactor)
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ALWAYS Detangle! NEVER Rewrite!
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(well, almost)
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Rewrite good code. Refactor tangled code.
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Wat? Rewrite good code?
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Rewrites are good for fixing performance and architecture bottlenecks
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Rewrites are tempting
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Coders want to Code!
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OMG guys, let’s rewrite this in Coffeescript and Ember and D3!!!
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Writing code is easier than reading code.
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You CANNOT rewrite code you don’t understand.
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Your rewrite will likely miss requirements
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In your client’s eyes, your rewrite will be worse than the original.
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What is Refactoring?
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Methodically improving code quality without altering behavior.
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Making your complex code simple.
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Simple code is...
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#1 Tested
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#2 Reveals Intent
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#3 DRY - Each piece of knowledge exists in only one place
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#4 Small
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87% of refactoring is improving naming
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What ISN’T Refactoring?
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Making changes to untested code is not refactoring.
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That’s just changing shit.
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Turning JS into Coffeescript is not refactoring.
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That’s just... silly.
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Let’s Start Detangling! Ready... Set...
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Before refactoring, you may take 30 seconds to rage.
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It’s cool, I’ll wait.
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Okay, now STOP IT!
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You don’t know what forces affected this code, you might have done the same.
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A certain level of respect for the code is necessary.
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First Things First: Set a Goal
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How much code needs to be refactored? How deeply?
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Write a Test!
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Why write tests?
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Makes the code simple
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Ensures Behavior Does Not Change
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Forces Developer to Understand Requirements
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Defines the public API, if originally unclear
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Refactoring #1 Name the Anonymous Functions
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BEFORE
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Refactoring #2 Document Responsibilities with Comments
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“Comment Driven Refactoring” (patent pending)
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BEFORE
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Refactoring #3 Extract Methods
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Refactoring #4 Improve Variable Names
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Refactoring #5 Add Local Vars to Improve Legibility
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Keep Extracting Functions
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Refactoring #6 Add Clarity with Underscore.js
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Refactoring #7 Isolate Display Logic
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Refactoring #8 Isolate DOM Manipulation
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Refactoring #9 Hide “Private” Methods in Closures
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Refactoring #10 Scope Public Methods in Namespaces
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Refactoring #11 Use Nested Namespaces
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Refactoring #12 Extend Namespaces (Don’t Overwrite)
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Refactoring #13 DRY Up Namespace Initialization
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Got questions? @chrisjpowers