javascript - 有条件地隐藏类(class)

Question

我是 jQuery 的新手，我一直在努力完成以下任务:

我在 SharePoint 2013 中有两个下拉菜单。当在 Role 菜单中选择 WFE 值时，我希望 Environment 字段消失。

我无法验证是否选择了 WFE:

$().ready(function () {
    $('.Role').change(function () {
        if ($('.Role').val() = 'WFE') {
            $('.Environment').hide();   
            alert('Changed!');
        }
    });
});

和

<table cellpadding="5" cellspacing="5" bgcolor="black" >
    <tr >
        <td>
          <!--Environment is a drop down menu in SharePoint 2013---->
            <b>Environment</b><br>
            <span class="Fields Environment" data-displayName="Environment"></span>
        </td>

    </tr>
    <tr >
        <td>
         <!--Role is a drop down menu in SharePoint 2013---->
            <b>Role</b><br>
            <span class="Fields Role" data-displayName="Role"></span>
        </td>
   </tr>
</table>

我看了好几篇文章，一点线索也没有。感谢您的建议。

Answer 1

$('.Role').val() = 'WFE'

应该是

$('.Role').val() === 'WFE'

= 表示赋值，=== 表示严格的类型和值相等，这几乎总是您想要的! == 可以使用，但会咬你，因为它会进行静默隐式转换，这会引入很难发现的细微错误。显式总是比隐式好。

JavaScript Comparison Operators

JavaScript has both strict and type–converting comparisons. A strict comparison (e.g., ===) is only true if the operands are of the same type. The more commonly used abstract comparison (e.g. ==) converts the operands to the same Type before making the comparison. For relational abstract comparisons (e.g., <=), the operands are first converted to primitives, then to the same type, before comparison.

Strings are compared based on standard lexicographical ordering, using Unicode values.