主要就是为了监听键盘按下的是哪个键，并且转成ASCII码;
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>window.event.keyCode</title>
</head>
<body onkeydown=" alert(window.event.keyCode)">
<input id="txtCode" type="text" />
</body>
</html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>window.event.keyCode</title>
</head>
<body onkeydown=" alert(window.event.keyCode)">
<input id="txtCode" type="text" />
</body>
</html>
那么如何用回车代替小键盘的回车呢？首先我们要知道，回车的ASCII码是13 ，TAB键的ASCII码是9那就好办啦；
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>使用回车代替TAB键</title>
</head>
<body onkeydown="if(window.event.keyCode==13){ window.event.keyCode=9}">
<input id="txtCode" type="text" />
<input id="txtCode2" type="text" />
</body>
</html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>使用回车代替TAB键</title>
</head>
<body onkeydown="if(window.event.keyCode==13){ window.event.keyCode=9}">
<input id="txtCode" type="text" />
<input id="txtCode2" type="text" />
</body>
</html>
在上面的代码中我们使用了keyCode来实现回车代替TAB键，只是简单的做了一个判断，如果当按下的是回车（13），我们就把TAB（9）的值赋给它（骗骗计算机），这些小小的细节积累起来，也是一批不小的财富吧！
下面接着写点东西，算是一个完整的示例吧；一个金融软件中文本框只能输入数字，和方向键，删除键等（代码中不是很严谨，仅供参考）
<!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>
<title>金融软件文本框禁用非法字符特效-2011-04-26</title>
<style type="text/css">
.ime
{
ime-mode: disabled; /**只对IE有效，禁用输入法切换**/
width:300px;
}
</style>
<script language="javascript" type="text/javascript">
function isValiNum(k) {
return (k == 9 || k == 13 || k == 46 || k == 8 || k == 189 || k == 190 || k == 110 || (k >= 48 && k <= 57) || (k >= 96 && k <= 105) || (k >= 37 && k <= 40));
}
function numKeyDown() {
var k = window.event.keyCode;
//判断输入字符是否合法；调用isValiNum函数；
return isValiNum(k);
}
function numPaste() {
//从剪切板中获取数据；
var text = window.clipboardData.getData("Text");
for (var i = 0; i < text.length; i++) {
var asc = text.charCodeAt(i); //转成ASCII值；
if (!isValiNum(asc)) {
return false;
}
}
}
//自动给输入的数据加逗号；
function commafy(n) {
var re = /\d{1,3}(?=(\d{3})+$)/g;
var n1 = n.replace(/^(\d+)((\.\d+)?)$/, function (s, s1, s2) { return s1.replace(re, "$&,") + s2; });
return n1;
}
</script>
</head>
<body>
<input id="txtCode" type="text" class="ime" onpaste="return numPaste()" onkeydown="return numKeyDown()" onfocus="this.style.textAlign='left'; this.value=this.value.replace(/,/g,'');" onblur="this.style.textAlign='right';this.value=commafy(this.value)" />
</body>
</html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>金融软件文本框禁用非法字符特效-2011-04-26</title>
<style type="text/css">
.ime
{
ime-mode: disabled; /**只对IE有效，禁用输入法切换**/
width:300px;
}
</style>
<script language="javascript" type="text/javascript">
function isValiNum(k) {
return (k == 9 || k == 13 || k == 46 || k == 8 || k == 189 || k == 190 || k == 110 || (k >= 48 && k <= 57) || (k >= 96 && k <= 105) || (k >= 37 && k <= 40));
}
function numKeyDown() {
var k = window.event.keyCode;
//判断输入字符是否合法；调用isValiNum函数；
return isValiNum(k);
}
function numPaste() {
//从剪切板中获取数据；
var text = window.clipboardData.getData("Text");
for (var i = 0; i < text.length; i++) {
var asc = text.charCodeAt(i); //转成ASCII值；
if (!isValiNum(asc)) {
return false;
}
}
}
//自动给输入的数据加逗号；
function commafy(n) {
var re = /\d{1,3}(?=(\d{3})+$)/g;
var n1 = n.replace(/^(\d+)((\.\d+)?)$/, function (s, s1, s2) { return s1.replace(re, "$&,") + s2; });
return n1;
}
</script>
</head>
<body>
<input id="txtCode" type="text" class="ime" onpaste="return numPaste()" onkeydown="return numKeyDown()" onfocus="this.style.textAlign='left'; this.value=this.value.replace(/,/g,'');" onblur="this.style.textAlign='right';this.value=commafy(this.value)" />
</body>
</html>