{n: 1}

{n: 2}

undefined

ReferenceError

[1, 2, 3, 4, 6]

[1, 2, 3, 4, <2 empty items>, 6]

[1, 2, 3, 4, undefined, undefined, 6]

[1, 2, 3, 4, <2 nullable items>, 6]

[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