![String Theory// fourthattemptfunctionisString(v) {returnObject.prototype.toString. โcall(v) === ยด[object String]ยด;}// untilsomejokerchanges// Object.prototype.toString... :-/](https://image.slidesharecdn.com/talk-110530050008-phpapp01/85/JavaScript-WTFs-14-320.jpg)
![WTF?> [] == ![] <Array>[] == !<Array>[]<Array>[] == !ToBoolean(<Array>[]) <Array>[] == <Bool>false <Array>[] == ToNumber(<Bool>false) <Array>[] == <Number>0ToPrimitive(<Array>[]) == <Number>0<String>[].toString() ==<Number>0 <String>ยดยด == <Number>0](https://image.slidesharecdn.com/talk-110530050008-phpapp01/85/JavaScript-WTFs-16-320.jpg)
![Well, not foreverybody.for (franz=0;franz<items.length;franz++) { vare = items[franz];...](https://image.slidesharecdn.com/talk-110530050008-phpapp01/85/JavaScript-WTFs-19-320.jpg)
JavaScript WTFs
- 2. AboutmeRaphael PigullaBรถrseGo AGLead Developer [email protected]@muddyb0y
- 3. WTF?functionfoo() {return { bar: true}}// whatis x?var x = bar();
- 4. Semicolon Insertionfunctionfoo() {return; { bar: true;};}// whatis x?var x = bar();
- 5. Semicolon Insertion{ 1 2 } 3{ 1 2 } 3;โ{ 1;2;} 3;{ 12 } 3โi;++j;โi++j
- 6. WTF?varfoo = 42;function bar() {foo = 13;}// foois 42bar();// foois?
- 7. WTF?varfoo = 42;function bar() {foo = 13;varfoo;}// foois 42bar();// foois?
- 8. DeclarationHoistingvarfoo = 42;function bar() {returnfoo;varfoo = 17;}// whatisthereturnvalueof bar() ?bar();
- 9. FunctionScopevar x = 42;functionfoo(n) { x = 13;while (--n > 0) {var x = 2 * n;}}
- 11. String Theory// firstattemptfunctionisString(v) {returntypeof v === ยดstringยด;}isString(new String(ยดfooยด)); // false!
- 12. String Theory// secondattemptfunctionisString(v) {return v instanceof String;}isString(ยดoh dearยด); // false!
- 13. String Theory// thirdattemptfunctionisString(v) {returntypeof v === ยดstringยด || v instanceof String;}isString(popup.window.getSomeString());// mayreturnfalse
- 14. String Theory// fourthattemptfunctionisString(v) {returnObject.prototype.toString. โcall(v) === ยด[object String]ยด;}// untilsomejokerchanges// Object.prototype.toString... :-/
- 15. // untilsomeoneoverwrites String// orRegExp.test-.-String Theory// fifthattemptfunctionisString(v) {returntypeofv ===ยดstringยด ||!!v && /^function String\(\) {/โ .test(ยดยด + v.constructor);}
- 16. WTF?> [] == ![] <Array>[] == !<Array>[]<Array>[] == !ToBoolean(<Array>[]) <Array>[] == <Bool>false <Array>[] == ToNumber(<Bool>false) <Array>[] == <Number>0ToPrimitive(<Array>[]) == <Number>0<String>[].toString() ==<Number>0 <String>ยดยด == <Number>0
- 19. Well, not foreverybody.for (franz=0;franz<items.length;franz++) { vare = items[franz];...
- 20. โIt turns out thatif you haveabsolutelynoideawhatyouโredoing in thelanguage, you can still generallymakethingswork.โDouglas Crockford
- 23. Whydoesit matter?JavaScript iseverywhereyou needfirstclass JavaScript developersweeding out thedudsisdifficultjQuery โ JavaScriptjQuery
- 24. The ChecklistโขWhatisthedifferencebetween...closure vs.anonymousfunctionfunctionalvs. imperative languagesprototypicalvs.class-basedinheritanceasynchronousvs. multi-threadedcode
- 25. Source: @markrendle on Twitter