<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>Untitled Document</title>
<script type="text/javascript">
function showcontent(){
document.getElementById("second").value=document.getElementById("first").value;
}
</script>
</head>
<body>
<input type="text" name="first" id="first" onkeydown="showcontent()" />
<input type="text" name="second" id="second" />
</body>
</html>
但好似会少显示一个字符。必须使用onkeyUP事件