1、数字数组转化为字符串数组
var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
arr.map(String); //结果: ['1', '2', '3', '4', '5', '6', '7', '8', '9']
2、字符串数组转化为数字数组
var a = ['1', '2', '3', '4', '5', '6', '7', '8', '9']
a.map(Number); //结果:[1, 2, 3, 4, 5, 6, 7, 8, 9]