0,1,2,3,4,5,6

0,1,2,3,4,5,6


0,1,2,3,4,5,6


8,9,10

8,9,10

11,12
8,9,10
11,12


11,12

11,12,8,9,11,12

11,12,8,9,11,12,8,9,11,12

11,12,8,9,11,12,8,9,11,12,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9
11,12
11,12,8,9,11,12,8,9,1,2,3,4,5,6,7,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9
12,8,9
11,[object Object],hello,11,12,8,9,1,2,3,4,5,6,7,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9,8,9
6
1
9
9,10,11,12,2,3,4,5,6
0

6
4,5,6
4
1,2,3,7
0
undefined
hello world
undefined
hello world
undefined
hello world
Test: splice when the item to replace is not writable.
e instanceOf TypeError = true
a.length = 2
arr.length = 12