<script>
function cal()
{
var rem=document.myform.txtr.value;
document.myform.txtf.value=rem;
}
</script>
</head>
<body>
<form action="" method="get" name="myform">
<input name="txtr" type="text">
<input name="txtf" type="text">
<input name="" type="button" value="确定">
</form>