写网页,一个题目,4个选项(用单选按钮实现),一个提交按钮,选择答案之后点击提交按钮,用JS判断是否正确

Question

题目是选一个偶数（A.1，B.3，C.2， D.5）用JavaScript判断是不是选对了，求帮忙啊，初学JS搞不明白啊

Answer 1

<dl>
        <dt>1.选择一个偶数</dt>
        <dd>
            <label><input type="radio" name="radio" value="1">A.1</label>
            <label><input type="radio" name="radio" value="3">A.3</label>
            <label><input type="radio" name="radio" value="2">A.2</label>
            <label><input type="radio" name="radio" value="5">A.5</label>
        </dd>
        <a href="javascript:;" class="formBtn">提交</a>
</dl>
<script type="text/javascript">
    document.getElementsByClassName('formBtn')[0].onclick = function(){
        var radio = document.getElementsByName('radio'),vals=null;
        for(var i=0;i<radio.length;i++){
            if(radio[i].checked){
                vals=radio[i].value;
                (radio[i].value%2==0)? alert('正确'):alert('错误');
            }
        }  
        if(vals==null){
            alert('请选择答案后再提交')
        }  
    }
</script>

Answer 2

<input type="radio" name="radio" value="1">A.1
<input type="radio" name="radio" value="3">B.3
<input type="radio" name="radio" value="2">C.2
<input type="radio" name="radio" value="5">D.5
if($('input:radio:checked').val() == 2){alert('正确') } else{'alert('错误')}

Answer 3

有使徒行者2？