用javascript验证表单

我正试图让验证过程使用javascript,我的表单有四个单选按钮和一个提交按钮,我想让它这样,如果用户单击提交,没有选择任何单选按钮,那么它会弹出一个警告,不提交表单。我的表格是这样的:

<form method="post" name="inform">
If you checked off <span style="text-decoration:underline">any</span> problems, how  <span style="text-decoration:underline">difficult</span> have these problems made it for you to do your work take care of things at home or get along with other people?
<table id="lastquestion">
<tr>
<td>Not difficult at all</td>
<td>Somewhat difficult</td>
<td>Very difficult</td>
<td>Extremely Difficult</td>
</tr><tr>
<td style="text-align:center"><input type="radio" value="not difficult at all" name="finalquestion" /></td>
<td style="text-align:center"><input type="radio" value="somewhat difficult" name="finalquestion" /></td>
<td style="text-align:center"><input type="radio" value="very difficult" name="finalquestion" /></td>
<td style="text-align:center"><input type="radio" value="extremely difficult" name="finalquestion" /></td>
</tr>
</table>
<input type="hidden" value="<?php echo $totalScore; ?>" name="totalScore" />
<input type="submit" value="Submit Final Answer" name="submit" onclick="return validate(inform)" />
</form>

下面是脚本的样子:

function validate(formCheck)
{
    if(formCheck.finalquestion == "")
    {
        alert("Please Choose an option");
        return false;
    }
    else
    {
        return true;
    }
}

但由于某种原因,我的按钮正在提交无论什么,这里的任何建议都会有所帮助,谢谢!

更新:我试过选择一个收音机,然后在validate函数和formcheck中发出警报。最后一个问题打印出来了:【对象节点列表】,所以我认为选择哪个按钮的值不会正确通过。