<!DOCTYPE html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>untitled</title> <script type="text/javascript"> function testContent(obj){ if(document.getElementById(obj).value.length==0){ alert('不能为空');return false; } } </script> </head> <body> <form name="search" method="post" action=""> <input name="input" id="test"> <input type="button" name="go" value="goSearch" onClick=" return testContent('test')"> </form> </body> </html>