源代码:
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Wfuyu教程(wfuyu.com)</title> </head> <body> <script> var txt="Hello World!"; document.write("<p>" + txt.toUpperCase() + "</p>"); document.write("<p>" + txt.toLowerCase() + "</p>"); document.write("<p>" + txt + "</p>"); </script> <p>该方法返回一个新的字符串，源字符串没有被改变。</p> </body> </html>
运行结果：