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Episode 2 of 9 · The interview course

JavaScript interview: types, coercion and equality

Chapters

1. How many types are there0:00
2. The seven primitives0:16
3. Typeof, in full0:35
4. Typeof null is a bug0:52
5. Two different nothings1:08
6. Undefined against null1:25
7. What makes not a number1:45
8. The only value unequal to itself2:03
9. Testing for it, correctly2:18
10. Object.is, the third one2:32
11. Why floats disagree2:49
12. The eight falsy values3:07
13. Or against nullish3:24
14. Implicit and explicit3:42
15. Plus is two operators4:00
16. The other operators disagree4:15
17. ParseInt and its radix4:33
18. Plus with arrays and objects4:49
19. Strict against abstract5:07
20. The four rules that matter5:27
21. Equality is not transitive5:43
22. Null against zero6:03
23. The showpiece6:20
24. Arrays becoming primitives6:37
25. The wrapper, loosely6:56
26. The wrapper, strictly7:14
27. Two wrappers, still false7:31
28. Why boxing exists7:49
29. Delete leaves a hole8:04
30. Holes, and what skips them8:20
31. Which check when8:37
32. A reference, not a value8:57
33. Why two identical objects differ9:11
34. The stringify shortcut9:26
35. The three ways it lies9:44
36. Writing deep equal10:02
37. Copying, shallowly10:18
38. Where shallow bites10:35
39. A real deep copy10:52
40. Which array methods mutate11:13
41. Symbol, WeakMap, null prototype11:30
42. Map against forEach11:47
43. Neither one can be stopped12:03
44. Filter, find, some, every12:18
45. When reduce is the answer12:36
46. Sort sorts as strings12:51
47. The worked example: map13:09
48. The worked example: filter, reduce13:26
49. The worked example: sort, group13:44
50. The one rule13:59

JavaScript interview: types, coercion and equality. Two days from an interview, and this question opens most of them. How many types does JavaScript have. Eight. Seven primitives and one object type. Say the number first, then the l

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