1s = { 1, 2, 3, 4, 5, 6 }
 2print(#s)     -- output: 6
 3s[4] = nil
 4print(#s)     -- output: 6
 5s[7] = nil
 6print(#s)     -- output: 3
 7s[4] = 4
 8print(#s)     -- output: 6
 9s[4] = nil
10print(#s)     -- output: 3
11
12print()
13
14s = { "1", "2", "3", "4", "5", "6" }
15print(#s)     -- output: 6
16s["4"] = nil
17print(#s)     -- output: 6
18s["7"] = nil
19print(#s)     -- output: 6
20s["4"] = "4"
21print(#s)     -- output: 6
22s["4"] = nil
23print(#s)     -- output: 6

Lua 5.3.4

输出就是这么匪夷所思,所以, 不要在Lua的table中使用nil值，如果一个元素要删除，直接remove