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Kevin Whinnery: Write Better JavaScript
The document provides insights into JavaScript, highlighting both its strengths and weaknesses, and offers tips on object-oriented programming and useful coding patterns. It emphasizes the importance of understanding JavaScript's prototypal inheritance and offers style guidelines to improve code quality. Additionally, it discusses JavaScript's role in mobile development using Titanium and provides further reading resources for developers.
Kevin Whinnery: Write Better JavaScript
- 1. Write Better JavaScript Kevin Whinnery
- 2. Kevin Whinnery Engineer andPlatform Evangelist Appcelerator since 2008 Husband and father of three: Web developer and JavaScript slinger turned mobile and desktop hacker. http://kevinwhinnery.com http://twitter.com/kevinwhinnery http://github.com/kwhinnery
- 3. Agenda • The GoodParts and Bad Parts • Object-Oriented Programming in JavaScript • Useful JavaScript Patterns, Tricks, and Style Guidelines • JavaScript in Titanium Mobile • Further Reading
- 4. JavaScript is a tragically misunderstood language.
- 5. “JavaScript is the incredibly hot girl at the party that brings her loser boyfriend DOM” Tom Robinson Founder, 280 North
- 6. JavaScript – Whatis it good for? • Absolutely nothing? Far from it… • Object-Oriented (Prototypical Inheritance)… or not • Flexible Objects • First-Class Functions • Built for event-driven UI
- 7. JavaScript: The GoodParts • Published In 2008 by Doug Crockford • Covers the good and bad • I use patterns from this book every time I write JS • Buy/read/love
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- 9. Global Variables app.js some/library.js
- 10. Truthy and Falsy • Falsy Values: • false • 0 • ‘’ • null • undefined • NaN • Truthy Values: • Everything else • Almost always, you want === and !==
- 11. Floating Point Arithmetic Avoid this by converting to whole numbers, and converting back to decimal.
- 12. typeof is aliar
- 13. there’s more (http://wtfjs.com), but let’s skip to…
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- 20. …plus it’s EVERYWHERE. onecould develop all kinds of software applications with nothing else.
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- 22. JavaScript has PrototypalInheritance, which creates new copies of objects from an existing object (the prototype) there’s much more to it than this, but we’ll keep it mostly high level…
- 23. Object Constructors * The capital first letter is by convention, not requirement.
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- 25. we could havealso wrote…
- 26. …but object instantiationusing the prototype to define functions/ properties is faster. http://ejohn.org/blog/simple-class-instantiation mentions this and other methods for…
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- 28. JavaScript doesn’t supportmultiple inheritance, but there are multiple libraries that handle that and more, including underscore.js http://documentcloud.github.com/underscore/#extend
- 29. Parasitic Inheritance • Createan existing object • Add new features and functionality to it (the parasites, if you will) • Pass it off as an instance of a new object • Slightly slower than .prototype but more flexible (and inescapable in certain cases)
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- 32. Self-Calling Function • Functionscope is the only scope in JavaScript • Self-calling function provides encapsulation • Both forms at right are valid, second is preferred
- 33. Module Pattern • Necessaryfor <script> in the browser or Ti.include • Uses functional scope to provide a public interface to a module • Tweetanium/ Training demos use a version of this
- 34. Dynamic Function Signatures • Not necessary to explicitly name parameters • Function interfaces can rationalize many input types • jQuery does this well, and is very popular b/c of its API
- 35. Call And Apply • Functions are first class objects • Passable, and callable • Can replace “this” inside function with something more useful • call: call a function with known arguments • apply: call a function with an array of arguments
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- 38. A More Useful“this”
- 39. Style Guidelines
- 40. Style “Dos” • Usedescriptive variable names (exception: well- understood, frequently typed modules/libraries, like “Ti” or “_” for Underscore.js) • JavaScript file contents (cohesion) • Google Style Guidelines: http://bit.ly/g_style • Follow the above and you are good to go
- 41. Style “Don’ts” • terselocal variable names – excuse me if I don’t know what “tvr” means inside your 300 line constructor • Huge files – if you want to write 13,000 lines in a file, go back to enterprise Java • Semicolons are not optional – you don’t want the interpreter writing code for you • and these monstrosities…
- 42. Curly braces onthe next line *this style will actually break in some environments (semicolon insertion)
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- 45. JavaScript Engines • iOS– JavaScriptCore – C-based, pretty darn fast • Android – Rhino – Java-based, meant for the server-side or desktop, just okay in terms of performance • Coming soon – Android/V8 – C-based, super duper fast, minimum Android version 2.2 (don’t freak out, check the version distribution stats) • Android: Very important not to load all scripts up front in large applications (slow)
- 46. Titanium Features • Built-inJSON serialization • CommonJS Module Spec • Proxy objects are special – what’s a proxy? A stand-in for a native object, like anything you get back from something like:
- 47. What’s special aboutproxies? • You can’t modify the prototype • You can’t add functions or properties that start with “get” or “set” – these are magic in Titanium proxies:
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- 49. Books and Reference • Mozilla Developer Network JavaScript Reference • JavaScript: The Good Parts • Eloquent JavaScript (free!) • High Performance JavaScript • JavaScript Patterns
- 50. Not Exhaustive “MustFollow” List • @kevinwhinnery J • @BrendanEich • @functionsource • @dalmaer • @thomasfuchs • @zacharyjohnson • @wycats • @DavidKaneda • @rem • @dawsontoth (Titanium goodness)
- 51. Potpourri • http://javascriptweekly.com -seriously, stop what you’re doing and go there right now • http://badassjs.com - then, after that, go here • http://jsbin.com - handy test harness • https://github.com/cjohansen/juicer - Great compression and obfuscation utility (Ruby) • http://crockford.com - Pay your respects
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