梦之都
JavaScript教程
undefined
属性，表示未定义的值
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>JavaScript undefined 属性示例</title> </head> <body> <script type="text/javascript"> var str; document.write(str); </script> </body> </html>