1,HTML source code£º <html> <head> <title>How to use StringBuffer</title> </head> <body> <script src="jsjava.js"></script> <script> var sb=new StringBuffer("Beijing"); document.write(sb+"<br>"); sb.append(" is"); document.write(sb+"<br>"); sb.append(" the capital of China"); document.write(sb+"<br>"); var des=sb.substringBetween(0,7); document.write(des); </script> </body> </html> 2,The display:

Beijing
Beijing is
Beijing is the capital of China
Beijing