<html>
<head>
<meta charset="utf-8">
</head>
<body>
<script language=javascript>
var oT1=document.getElementById('t1');
var oT2=document.getElementById('t2');
var oT3=document.getElementById('t3');
var oT4=document.getElementById('t4');
function t1_onkeyup() {
if(document.card.t1.value.length==4){
document.card.t2.focus();
}
}
function t2_onkeyup() {
if(document.card.t2.value.length==4){
document.card.t3.focus();
}
}
function t3_onkeyup() {
if(document.card.t3.value.length==4){
document.card.t4.focus();
}
}
</script>
<form name=card>输入字符：<input language=javascript
onkeyup="t1_onkeyup()" maxlength=4 size=4 id=t1>- <input
language=javascript onkeyup="t2_onkeyup()" maxlength=4 size=4
id=t2>- <input language=javascript onkeyup="t3_onkeyup()"
maxlength=4 size=4 id=t3>- <input maxlength=4 size=4 id=t4>
</form>
</body>
</html>
script language=javascript
这个不对，应该是type=javascript
代码都堆在一起了，谁看得清。建议分行写
oT1.value
代码放控件下面，放前面对象还没生成呢，获取的是null，或者放到window.onload事件中执行才行
<html>
<head>
<meta charset="utf-8">
</head>
<body>
<form name=card>输入字符：<input language=javascript
onkeyup="t1_onkeyup()" maxlength=4 size=4 id=t1>- <input
language=javascript onkeyup="t2_onkeyup()" maxlength=4 size=4
id=t2>- <input language=javascript onkeyup="t3_onkeyup()"
maxlength=4 size=4 id=t3>- <input maxlength=4 size=4 id=t4>
</form>
<!---------------放下面---------------------------->
<script language=javascript>
var oT1=document.getElementById('t1');
var oT2=document.getElementById('t2');
var oT3=document.getElementById('t3');
var oT4=document.getElementById('t4');
function t1_onkeyup() {
if(oT1.value.length==4){
oT2.focus();
}
}
function t2_onkeyup() {
if(oT2.value.length==4){
oT3.focus();
}
}
function t3_onkeyup() {
if(oT3.value.length==4){
oT4.focus();
}
}
</script>
</body>
</html>