Mega Code Archive
Use do-while loop and prompt dialog to restrict user input
<![CDATA[
<html>
<head>
<title>A Simple Page</title>
<script language="JavaScript">
do {
sometext = prompt("Enter some text","Type some text");
}
while (sometext == "Type some text" || sometext == "" || sometext == null);
alert(sometext);
</script>
</head>
<body>
</body>
</html>
]]>