list from

the good and bad bits of JavaScript

20. Detect data type in JavaScript

23. create a sum()

26. implement Object.assign()

27. implement completeAssign()

36. create a fake timer(setTimeout)

38. implement `jest.spyOn()`

39. implement range()

53. write your own `extends` in es5

60. create your own `new` operator

61. create your own `Function.prototype.call`

65. add comma to number

83. create an interval

84. create a fake timer (setInterval)

88. support negative Array index in JavaScript

90. write your own `instanceof`

94. implement your own `Object.create`

99. extract all anchor element from HTML string

101. merge identical API calls

119. create a tokenizer

135. localStorage with expiration