设置VSCode快捷键Alt+U(首字母转换为大写)、Shift+Alt+U(全部转换为大写)、Shift+Alt+L(全部转换为小写), 等同于'aaa'.replace(/^./,'aaa'.slice(0,1).toUpperCase());//Aaaaaa'.toUpperCase();//AAA等同于'AAA'.toLowerCase();//aaa