var data=[7,8,9];
"0" in data;//true
"1" in data;//true
"2" in data;//true
"3" in data;//false
0 in data;//true
1 in data;//true
2 in data;//true
3 in data;//false
加引号与不加引号都是代表下标吗?
"0" in data;//true
"1" in data;//true
"2" in data;//true
"3" in data;//false
0 in data;//true
1 in data;//true
2 in data;//true
3 in data;//false
加引号与不加引号都是代表下标吗?
数组长度为3,data[3]当然不存在了,0,1,2...
alert(a[0]===a['0']);
a['0'] = 100;
alert(a[0]);