<script language="javascript">... function CheckMyForm() ...{ var txt = myform.mytext.value; if(checknumber(txt)) ...{ alert("只允许输入数字!"); return false; } return true; } function checknumber(String) ...{ var Letters = "1234567890."; var i; var c; for( i = 0; i < String.length; i ++ ) ...{ c = String.charAt( i ); if (Letters.indexOf( c ) ==-1) ...{ return true; } } return false; } </script> <body> <form name="myform" onSubmit="return CheckMyForm()"> <input type="text" name="mytext"> <input type="submit" name="mysubmit"> </form> </body>