Javascript 中的 element 对象

element 对象：

<!DOCTYPE html>
<html>
  <head>
    <title>js22.html</title>
    <script type="text/javascript">
        function moveNext(object, index)
        {
            if (object.value.length == 4)
            {
                document.forms[0].elements[index+1].focus();
            }
        }
        function showResult()
        {
            var f = document.forms[0];
            var result = "";
            for (var i = 0; i<4; i++)
            {
                result += f.elements[i].value;
            }
            alert(result);
        }
    </script>
    
  </head>
  
  <body onload="document.forms[0].element[0].focus();">
    <form>
        <input type = "text" size= "3" maxlength = "4" onkeyup="moveNext(this,0);">-
        <input type = "text" size= "3" maxlength = "4" onkeyup="moveNext(this,1);">-
        <input type = "text" size= "3" maxlength = "4" onkeyup="moveNext(this,2);">-
        <input type = "text" size= "3" maxlength = "4" onkeyup="moveNext(this,3);">
        
        <input type="button" value="显示" onclick="showResult();">
    </form>
    
    
  </body>
</html>

结果就是：

1. 输入完第一个 text field 之后，会自动跳转到下一个 text field.

2. 点击显示按钮，会弹出输入的所有 text