Run ยป
<html> <body> <input type="text" id="txt" onkeyup="manage(this)" /> <input type="submit" id="btSubmit" disabled /> <script> function manage(txt) { var bt = document.getElementById('btSubmit'); if (txt.value != '') { bt.disabled = false; } else { bt.disabled = true; } } </script> </body> </html>