You don't know JavaScript

Transcript

1. You don’t know JavaScript @C1nde
3. >>> study[0] simple math
4. >>> [] + [] ""
5. >>> [] + [] "" >>> {} + {} NaN
6. >>> [] + [] "" >>> {} + {} NaN >>> [] + {} "[object Object]"
7. >>> [] + [] "" >>> {} + {} NaN >>> [] + {} "[object Object]" >>> {} + [] 0
8. >>> study[1] Boolean
9. >>> if (true) { console.log('Will be printed'); } >>> if (false) { console.log('Will not be printed'); }
10. >>> if (new Boolean(false)) { console.log('hmmmm'); } hmm
11. >>> if (new Boolean(false)) { console.log('hmmmm'); } hmm >>> if (Boolean(false)) { console.log('as expected'); }
12. >>> study[2] NaN
13. >>> isNaN(new Date()); false >>> isNaN(new Date('notADate')); true
14. >>> isNaN(null); false
15. >>> isNaN(null); false >>> isNaN(undefined); true
16. >>> isNaN(null); false >>> isNaN(undefined); true >>> undefined == NaN; false
17. >>> isNaN(null); false >>> isNaN(undefined); true >>> undefined == NaN; false >>> NaN == NaN; false
18. >>> study[3] Object
19. >>> var o = {}; >>> typeof o "object"
20. >>> var o = {}; >>> typeof o "object" >>> o instanceof Object true
21. >>> typeof null "object"
22. >>> typeof null "object" >>> null instanceof Object false
23. >>> study[3] Object^W Null
24. >>> study[4] RegEx
25. >>> var lowerCaseOnly = /^[a-z]+$/;
26. >>> var lowerCaseOnly = /^[a-z]+$/; >>> lowerCaseOnly.test('a'); true >>> lowerCaseOnly.test('A'); false >>> lowerCaseOnly.test(''); false
27. >>> var lowerCaseOnly = /^[a-z]+$/; >>> lowerCaseOnly.test(null); true >>> lowerCaseOnly.test(undefined); true >>> lowerCaseOnly.test(); true
28. >>> study[5] String
29. >>> 'a string' === 'a string' true
30. >>> 'a string' === 'a string' true >>> new String('a string') === 'a string' false
31. >>> 'a string' === 'a string' true >>> new String('a string') === 'a string' false >>> String('a string') === 'a string' true
32. >>> study[6] String & RegEx
33. >>> var address = 'http://storage. com/gifs/picture.jpg'; >>> address.match('.gif');
34. >>> var address = 'http://storage. com/gifs/picture.jpg'; >>> address.match('.gif'); /gif
35. >>> study[7] Object
36. >>> var obj = { its: 1, an: 2, obj: 3 }; >>> obj.its = null; >>> obj.an = undefined; >>> delete obj.obj;
37. >>> for(var item in obj) { if (obj.hasOwnProperty(item)) { console.log(item, obj[item]); } } its null an undefined
38. >>> study[8] prototype
39. >>> var obj = {}; >>> var proto = Object.prototype; >>> proto.isPrototypeOf(obj); false >>> Object.isPrototypeOf(obj); false
40. >>> var obj = new Object(); >>> var proto = Object.prototype; >>> proto.isPrototypeOf(obj); false >>> Object.isPrototypeOf(obj); false
41. >>> var obj = {}; >>> var proto = Object.prototype; >>> proto === Object.getPrototypeOf (obj); true
42. >>> study[9] ???
43. >>> undefined == null; true
44. [~] > cat check.coffee obj = prop: value if obj.prop? console.log obj.prop [~] > coffee -b -p check.coffee var obj; obj = { prop: value }; if (obj.prop != null) { console.log(obj.prop); }
45. THANKS