Actually, this is an ongoing problem. While Andy is right about the downloaded source, .val(...) and .attr('value',...) don't seem to actually modify the html. I think this is a javascript problem and not a jquery problem. If you had used firebug even you would have had the same question. While it seems that if you submit the form with the modified values it will go through, the html does not change. I ran into this issue trying to create a print preview of the modified form (doing [form].html()) it copies everything okay, including all changes except values changes. Thus, my modal print preview is somewhat useless... my workaround may have to be to 'build' a hidden form containing the values they have added, or generate the preview independently and make each modification the user makes also modify the preview. Both are inoptimal, but unless someone figures out why the value-setting behavior does not change the html (in the DOM i'm assuming) it will have to do.

我也有同样的问题，我找到了问题所在。我把HTML定义为

<form action="url" method="post">
    <input type="hidden" id="email" />
<form>
<script>
    function onsomeevent()
    {
       $("#email").val("a@a.com");
    }
</script>

在服务器上读取表单值总是导致电子邮件为空。在绞尽脑汁(和无数次搜索)之后，我意识到错误在于没有正确定义表单/输入。在修改输入时(如下所示)，它就像一个咒语一样有效

<input type="hidden" id="email" name="email" />

添加到这个线程，以防其他人有同样的问题。

在我的情况下，我使用了一个非字符串(整数)作为val()的参数，这并不管用，技巧就像

$("#price").val('' + price);

又有人在这里抓你了，浪费了我的时间，所以我想我应该把这个建议给你。我有一个隐藏字段，我给了一个id。名称中的[]括号(由于与struts2一起使用)和选择器$(“#model.thefield[0]”)不会找到我的隐藏字段。将id重命名为不使用句号和括号会导致选择器开始工作。因此，最后我以model_the_field_0的id代替，选择器工作正常。

<javascript>


slots=''; hidden=''; basket = 0;

    cost_per_slot = $("#cost_per_slot").val();
    //cost_per_slot = parseFloat(cost_per_slot).toFixed(2)

    for (i=0; i< check_array.length; i++) {
        slots += check_array[i] + '\r\n';
        hidden += check_array[i].substring(0, 8) + '|';
        basket = (basket + parseFloat(cost_per_slot));
    }

    // Populate the Selected Slots section
    $("#selected_slots").html(slots);

    // Update hidden slots_booked form element with booked slots
    $("#slots_booked").val(hidden);     

    // Update basket total box
    basket = basket.toFixed(2);
    $("#total").html(basket);

如果你在设置一个隐藏字段的值时遇到了麻烦，因为你传递了一个ID给它，这是解决方案:

用$("input[id=hidden_field_id]").val(id)代替$("#hidden_field_id").val(id)。不知道有什么区别，但确实有效。