[2, NaN, NaN, 2]

[2, 2, 2, 2]

[NaN, NaN, NaN, NaN]

[2, undefined, undefined, 2]

JavaScript JavaScript

It's JavaScript

undefined, JavaScript

Error

1

undefined

Error

window

"ab"

"abe"

"abcde"

"undefined"

1 2 3 4

2 4 1 3

2 1 4 3

4 3 2 1

1, 7, 3, 5, 2, 6, 4

1, 7, 3, 5, 2, 4, 6

1, 3, 5, 7, 2, 6, 4

1, 7, 3, 5, 4, 2, 6

1

undefined

Error

null

5, 5, 15, 25

5, 25, 15, 10

5, 25, 15, 15

5, 5, 15, 15

6 2 1 5 7 3 8 4

6 2 1 3 5 7 4 8

6 2 1 3 4 8 5 7

6 2 1 3 8 4 5 7

9

10

11

12