Fighting Boolean Traps

Presented at WaffleJS meetup. Jan 10, 2018. San Francisco.

Ever encounter some code that looks like new Slider(true /*horizontal*/)? Perhaps you are confused by the semantics exhibited by setState(true, false)? Did you get a headache when trying to unpack double negatives as in filter.caseInsensitive = false? These are typical API blunders often denoted as Boolean Traps. Learn how to recognize such a mistake and also more importantly, how to prevent it from happening!

Transcript

1. Fighting Boolean Traps
2. Readable, consistent, crystal clear Thank you, Captain Obvious!
3. https://twitter.com/AriyaHidayat/status/455892955765551105
4. I HAVE A BAD FEELING ABOUT THIS…
5. A long time ago in a galaxy far far away…
6. var powerSlider = new Slider();
8. var anotherSlider = new Slider(false);
9. IT’S A TRAP!
10. IT’S A BOOLEAN TRAP!
11. s2 = new Slider(false); s1 = new Slider(true);
12. s2 = new Slider(false /*horiz*/); s1 = new Slider(true /*vertical*/);
13. Code is written once, read many times.
14. s1 = new Slider({ orientation: "vertical" }); s2 = new Slider({ orientation: "horizontal" });
15. s2 = new VerticalSlider(); s1 = new HorizontalSlider();
16. contacts.find(str);
18. // Check the cache first contacts.find(str, true); // Fresh search only contacts.find(str, false);
19. IT’S A MODIFIER TRAP!
20. the more the merrier
21. Ping-pong, Anyone? // Expand + animate treeItem.setState(true, true); // Expand + don't animate treeItem.setState(true, false); // Collapse + animate treeItem.setState(false, true);
22. DOM Event event.initKeyEvent("keypress", true, true, null, null, false, false, false, false, 9, 0);
23. Double Negatives X.disabled = false; Y.setHidden(true); filter.caseInsensitive = true; X.enabled = true; Y.setVisible(false); filter.caseSensitive = false;
24. picker.yearFrom = 1980; picker.yearTo = 2020; picker.minimumYear = 1980; picker.maximumYear = 2020;
25. this.callMe = "Adam"; flight.from = SFO; flight.to = JFK; this.name = "Adam"; flight.departure = SFO; flight.destination = JFK;
26. var x = Math.sqrt(-2) isNaN(x) true x === NaN false isNaN('hola') true x == NaN false
27. https://twitter.com/AriyaHidayat/status/393034774245171200
28. GarlicNaN != NaN Future JavaScript?
29. Best Practices
30. #1: Private by Default Public = Irreversible
32. SHStripMneumonic “Why is the function SHStripMneumonic misspelled?” Raymond Chen, Microsoft http://blogs.msdn.com/b/oldnewthing/archive/2008/05/19/8518565.aspx
33. -- yours truly “You’d fail your first two attempts anyway.”
35. #2: Mandatory API Review
36. “Write 3 examples which use the API.”
37. #3: Build and Use TOOLS
38. Summary
39. Boolean traps (and other API mistakes) lead to FEAR
40. [Yoda]
41. Thank You Some artworks are from https://unsplash.com/ and http://openclipart.org. speakerdeck.com/ariya @ariyahidayat