js有效数字 显示指定位数

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head> <title>无标题页</title> </head> <script language="javascript" type="text/javascript"> var a = 0.123456789; document.write(a.toPrecision(3)); </script> <body> </body> </html>
[Ctrl+A 全选 注:如需引入外部Js需刷新才能执行]