jQuery val（）设置表单值时引发运行时错误

Question

我是Javascript / JQuery的新手，如果我错过了一些简单的内容，我们深表歉意。 我正在尝试创建一个按钮，以根据数量和单价计算总数，并用结果填充总数字段。 这是使用VS2010在ASP.NET MVC3中完成的。

我的代码似乎可以将SpoilageQuantity和SpoilageUnitPrice的值确定为OK，但无法设置SpoilageTotalPrice的值。 该错误表明我正在尝试为函数结果分配一个值，但是我的理解是val（）可用于获取和设置表单字段值。 更正或建议？

VS2010视图：

<div class="editor-label">
    @Html.LabelFor(model => model.SpoilageQuantity)
</div>
<div class="editor-field">
    @Html.EditorFor(model => model.SpoilageQuantity)
    @Html.ValidationMessageFor(model => model.SpoilageQuantity)
</div>

<div class="editor-label">
    @Html.LabelFor(model => model.SpoilageUnitPrice)
</div>
<div class="editor-field">
    @Html.EditorFor(model => model.SpoilageUnitPrice)
    @Html.ValidationMessageFor(model => model.SpoilageUnitPrice)
</div>

<div class="editor-label">
    @Html.LabelFor(model => model.SpoilageTotalPrice)
</div>
<div class="editor-field">
    @Html.EditorFor(model => model.SpoilageTotalPrice)
    @Html.ValidationMessageFor(model => model.SpoilageTotalPrice)
    <input type="button" value="Calculate" onclick="calculateTotal()" />
</div>

JS档案：

function calculateTotal() {
// calculate total spoilage price from unit price and quantity
var totalprice = $('#SpoilageQuantity').val() * $('#SpoilageUnitPrice').val();
totalprice = totalprice.toFixed(2);

$('#SpoilageTotalPrice').val(totalprice);
}

呈现的HTML：

<div class="editor-label">
        <label for="SpoilageQuantity">Item Quantity</label>
    </div>
    <div class="editor-field">
        <input class="text-box single-line" data-val="true" data-val-number="The field Item Quantity must be a number." data-val-required="Quantity of item lost is required." id="SpoilageQuantity" name="SpoilageQuantity" type="text" value="0.00" />
        <span class="field-validation-valid" data-valmsg-for="SpoilageQuantity" data-valmsg-replace="true"></span>
    </div>

    <div class="editor-label">
        <label for="SpoilageUnitPrice">Unit Price</label>
    </div>
    <div class="editor-field">
        <input class="text-box single-line" data-val="true" data-val-number="The field Unit Price must be a number." data-val-required="Unit price is required." id="SpoilageUnitPrice" name="SpoilageUnitPrice" type="text" value="0.00" />
        <span class="field-validation-valid" data-valmsg-for="SpoilageUnitPrice" data-valmsg-replace="true"></span>
    </div>

    <div class="editor-label">
        <label for="SpoilageTotalPrice">Total Price</label>
    </div>
    <div class="editor-field">
        <input class="text-box single-line" data-val="true" data-val-number="The field Total Price must be a number." data-val-required="The Total Price field is required." id="SpoilageTotalPrice" name="SpoilageTotalPrice" type="text" value="0.00" />
        <span class="field-validation-valid" data-valmsg-for="SpoilageTotalPrice" data-valmsg-replace="true"></span>
        <input type="button" value="Calculate" onclick="calculateTotal()" />
    </div>

错误信息：

Microsoft JScript runtime error: Cannot assign to a function result

编辑：整个js文件：

/*  Copyright 2012 Tom Barrett

This file is part of PFC Logs.

PFC Logs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

PFC Logs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with PFC Logs.  If not, see <http://www.gnu.org/licenses/>.
*/

function autoFocus() {
    // Auto-focus on the first text field upon page load.
    $("input[type=text]").first().focus();
}

function calculateTotal() {
    // calculate total from quantity & unit price
    var totalprice = $('#SpoilageQuantity').val() * $('#SpoilageUnitPrice').val();
    totalprice = totalprice.toFixed(2);
    $("#SpoilageTotalPrice").val(totalprice);
}

Answer 1

我不了解具体技术...但是我也遇到了这一点。 如果我的函数位于单独的js文件中，则我链接到我的标签中的jquery（或者与此有关的Jscript）找不到元素。 如果我将脚本包含在标签中，则一切正常。