在线运行代码 - 菜鸟教程

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(cainiaoplay.com)</title>
</head>
<body>

<p>在文本域达到最大字符时自动跳到下一个文本域：</p>
<form id="myForm">
<input type="text" size="3" tabindex="1" maxlength="3" onkeyup="myFunction(this,this.value)"> -
<input type="text" size="2" tabindex="2" maxlength="2" onkeyup="myFunction(this,this.value)"> -
<input type="text" size="3" tabindex="3" maxlength="3" onkeyup="myFunction(this,this.value)">
</form>
<script>
function myFunction(x, y) {
    if (y.length == x.maxLength) {
        var next = x.tabIndex;
        if (next < document.getElementById("myForm").length) {
            document.getElementById("myForm").elements[next].focus();
        }
    }
}
</script>

</body>
</html>
源代码

动行结果
