JavaScript字符串变大小写
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!