这样可以
<SCRIPT LANGUAGE="JavaScript">
<!--
function go()
{
var keycodeID=event.keyCode;
if(keycodeID == 13)
{
document.activeElement.value = document.activeElement.value+".00";
event.keyCode = 9;
}
}
//-->
</SCRIPT><body onkeydown="go();">
txt1:<INPUT TYPE="text" NAME="txt1" value='200'><br>
txt2:<INPUT TYPE="text" NAME="txt2" value='300'><br>
txt3:<INPUT TYPE="text" NAME="txt3" value='400'>
</body>
<SCRIPT LANGUAGE="JavaScript">
<!--
function go()
{
var keycodeID=event.keyCode;
if(keycodeID == 13)
{
document.activeElement.value = document.activeElement.value+".00";
event.keyCode = 9;
}
}
//-->
</SCRIPT><body onkeydown="go();">
txt1:<INPUT TYPE="text" NAME="txt1" value='200'><br>
txt2:<INPUT TYPE="text" NAME="txt2" value='300'><br>
txt3:<INPUT TYPE="text" NAME="txt3" value='400'>
</body>
{
Number.prototype.toFixed = function(d)
{
var s=this+"";if(s.indexOf(".")==-1)s+=".";s+=new Array(d+1).join("0");
if (new RegExp("^((-|\\+)?\\d+(\\.\\d{0,"+ (d+1) +"})?)\\d*$").test(s))
{
s="0"+ RegExp.$1, pm=RegExp.$2, a=RegExp.$3.length, b=true;
if (a==d+2){a=s.match(/\d/g); if (parseInt(a[a.length-1])>4)
{
for(var i=a.length-2; i>=0; i--) {a[i] = parseInt(a[i])+1;
if(a[i]==10){a[i]=0; b=i!=1;} else break;}
}
s=a.join("").replace(new RegExp("(\\d+)(\\d{"+d+"})\\d$"),"$1.$2");
}if(b)s=s.substr(1); return (pm+s).replace(/\.$/, "");} return this+"";
};
}alert(22.toFixed(2));
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>怎样把小数变成.00格式,判断回车后转到下个输入域</title>
<script type="text/javascript">
var transformData = function(textField){
var e = event;
var v = textField.value;
if(e.keyCode==13){
if(isNaN(parseInt(v))){
alert("not a number");
return;
}else{
if(v.indexOf(".")==-1){
textField.value = v+".00";
}
if(/[0-9]+\.[0-9]/.test(v)){
textField.value = v+"0";
}
if(/([0-9]+\.[0-9]{2})[0-9]*/.test(v)){
textField.value = v.replace(/([0-9]+\.[0-9]{2})[0-9]*/,"$1");
}
e.keyCode = 9;
}
}
}
</script>
</head>
<body>
<form action="" method="get">
<input type="text" id="num1" name="num1" onKeyDown="transformData(this);">
<input type="text" id="num2" name="num2" onKeyDown="transformData(this);">
<input type="text" id="num3" name="num3" onKeyDown="transformData(this);">
<input type="button" value="提交">
</form>
</body>
</html>