JS如何判断表单中用户选择哪个哪个选项？

JS如何判断表单中用户选择哪个哪个选项？

HTML代码：

<form name="form1" onsubmit="return foo();">

    A<input type="radio" name="radioGroup" value="a" />

    B<input type="radio" name="radioGroup" value="b" />

    C<input type="radio" name="radioGroup"   />

    D<input type="radio" name="radioGroup" />

    E<input type="radio" name="radioGroup" />

    F<input type="radio" name="radioGroup" />

    <input type="submit" />

  </form>

方法一：元素集合转换为数组实例，根据当前元素在数组中对应的索引位置判断元素。

    var aInput = document.getElementsByTagName("input");
    var arry = [];
    var nowIndex = null;
    for (var i = 0; i < aInput.length-1; i++) {
      arry[i] = aInput[i];
      aInput[i].onclick = function () {
        nowIndex = arry.indexOf(this);
        console.log("点击了第" + nowIndex + "个选项。");
      }
    }
    function foo() {
      alert(nowIndex+1);
    }

方法二：通过input元素的value值来判断点击的元素索引，缺陷是此方法不如第一种方法灵活，移植性较差。

    function foo() {
      alert(nowIndex+1)
    }
    var aInput = document.getElementsByTagName("input");
    var arry = [];
    var nowIndex = null;
    for (var i = 0; i < aInput.length-1; i++) {

      aInput[i].onclick = function () {

        var optValue = this["value"];
        switch (optValue) {
          case "a":
            nowIndex = 0;
            break;
          case "b":
            nowIndex = 1;
            break;
          case "c":
            nowIndex = 2;
            break;
          case "d":
            nowIndex = 3;
            break;
          case "e":
            nowIndex = 4;
            break;
          case "f":
            nowIndex = 5;
            break;
          default:
            nowIndex = null;
            ;

        }
        console.log("点击了第" + nowIndex + "个选项。");
      }
    }