var str = "hello world!";
var new_str = str.toUpperCase();
conlose.log(new_str);
HELLO WORLD!
new_str = str.toLowerCase();
hello world!
var str = "hello world!";
var new_str = str.toUpperCase();
conlose.log(new_str);
HELLO WORLD!
new_str = str.toLowerCase();
hello world!
转载于:https://www.cnblogs.com/liugangBlog/p/9765465.html