for ... in对Array的循环得到的是String而不是Number？

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#1 Created at ... [Delete] [Delete and Lock User]

var Ex=['a','b','c']; var idReg=/^[0-9]*$/;

for(var j in Ex){ if(idReg.test(j)){ alert(j+'is integer!'); }else alert(j+'is not integer'); }

我这么测试显示j是integer啊是不是我的代码写错了？

#2 Created at ... [Delete] [Delete and Lock User]

'use strict'; var arr = ['Bart', 'Lisa', 'Adam'];

for(var str in arr){

alert(typeof(str)); } 结果为string

#3 Created at ... [Delete] [Delete and Lock User]

你用正则来匹配j，本身就证明了j是字符串了啊？

#4 Created at ... [Delete] [Delete and Lock User]

数组也是对象，索引就是对象的属性，就是string，但是用的时候还是建议用整数