我在文本输入中使用占位符,效果很好。但我也希望在选择框中使用占位符。当然,我可以使用以下代码:

<select>
    <option value="">Select your option</option>
    <option value="hurr">Durr</option>
</select>

但“选择您的选项”是黑色而不是浅灰色。所以我的解决方案可能是基于CSS的。jQuery也很好。

这只会使下拉列表中的选项变灰(因此单击箭头后):

option:first {
    color: #999;
}

问题是:人们如何在选择框中创建占位符?但这已经得到了回应,欢呼。

使用此选项会导致所选值始终为灰色(即使在选择实际选项后):

select {
    color: #999;
}

当前回答

使用类名包,这里有一个与我的React功能组件一起工作的解决方案。我的组件使用钩子,但这可能对解决方案并不重要。这种方法是基于类的解决方案的一种功能性模仿。。。https://www.derpturkey.com/select-placeholder-with-react/

组件JS。。。

function NavBar(props, prevProps) {
            const ClassNames = require("classnames");  // package needs require rather than import
            const [where, changeWhere] = useState("");  // my component's value
            // classnames will add placeholderSelect class if chosen option's value is empty
            let whereClass = ClassNames("myOtherStyleRules", {
                placeholderSelect: !where,
            });
            ...
            return (
            ...
            <div id="where">
                            <select
                              className={whereClass}
                              value={where}
                              ...
                            >
                              <option value="" hidden> where? </option>    //  value must be empty, hidden from choice
                              <option value="24">Anchorage</option>
                              <option value="27">Birmingham</option>
                              <option value="28">Detroit</option>
                              <option value="25">Los Angeles</option>
                              <option value="26">Oahu</option>
                              <option value="29">Seattle</option>
                            </select>
                ... 

组件CSS。。。

        .placeholderSelect {
          color: rgb(167, 167, 167);
        }

其他回答

Angular 2的解决方案

在所选内容的顶部创建标签

<label class="hidden-label" for="IsActive"
    *ngIf="filterIsActive == undefined">Placeholder text</label>
<select class="form-control form-control-sm" type="text" name="filterIsActive"
    [(ngModel)]="filterIsActive" id="IsActive">
    <option value="true">true</option>
    <option value="false">false</option>
</select>

并应用CSS将其放置在顶部

.hidden-label {
    position: absolute;
    margin-top: .34rem;
    margin-left: .56rem;
    font-style: italic;
    pointer-events: none;
}

指针事件:none允许您在单击标签时显示select,当您选择选项时隐藏该选项。

角度html css

如果使用的是Angular,请执行以下操作:

<选择><option[ngValue]=“undefined”disabled selected>选择您的选项</option><option[ngValue]=“hurr”>Durr</option></选择>

由于本主题中提供的答案之间的样式和功能不同,下表阐明了所提供的HTML、HTML+CSS和HTML+CSS+Javascript解决方案的样式和适用的表单逻辑。

我不得不使用代码格式,因为出于某种原因,标记中不允许使用表。将使用代码段提供一个HTML表来解决表限制。

我将这篇文章标记为社区维基,这样任何人都可以详细介绍新的文章,但请将JQuery、React、Angular、CoffeeScript等添加到另一篇文章中,以保持此表的简单。

         | Technologies |                                                                Styling                                                                |
  Post   | CSS | Java-  | Select: Placeholder |  Select: valid option  |                  Option: placeholder                    |     Option: valid option     |
   ID    |     | script | Color |  Validation | Color |    Required    | Visibility | Selectable | Color |   Cond. formatting    | Color |   Cond. formatting   |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
41167307 | No  |   No   | Black |   Invalid   | Black |      Yes       |  Visible   |     No     | Grey  |          No           | Black |          No          |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
50200912 | No  |   No   | Black |    Valid    | Black |       No       | Invisible  |    N/A     |  N/A  |          No           | Black |          No          |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
5859221  | No  |   No   | Black |    Valid    | Black |       No       |  Visible   |     No     | Grey  |          No           | Black |          No          |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
38120777 | No  |   No   | Black |    Valid    | Black |       No       | Invisible  |    N/A     |  N/A  |          No           | Black |          No          |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
54860799 | Yes |   No   | Grey  |   Invalid   | Black |      Yes       | Invisible  |    N/A     |  N/A  |          No           | Black |          No          |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
52661024 | Yes |   No   | Grey  |   Invalid   | Black |      Yes       | Invisible  |    N/A     |  N/A  |          No           | Black | select:invalid{Grey} |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
8442831  | Yes |   No   | Grey  |   Invalid   | Black |      Yes       | Invisible  |    N/A     |  N/A  |          No           | Black | select:invalid{Grey} |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
29806043 | Yes |   No   | Grey  |   Invalid   | Black |      Yes       | Invisible  |    N/A     |  N/A  |          No           | Black |          No          |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
61966461 | Yes |   No   | Grey  |   Invalid   | Black |      Yes       | Invisible  |    N/A     |  N/A  | select:valid{visible} | Black |          No          |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
44406771 | Yes |   No   | Grey  |   Invalid   | Grey  |      No        |  Visible   |     No     | Grey  |          No           | Black | select:invalid{Grey} |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
40603035 | Yes |   No   | Black |    Valid    | Black |      No        | Invisible  |    N/A     |  N/A  |          No           | Black |          No          |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
22994211 | Yes |   No   | Grey  |    Valid    | Black |      No        | Invisible  |    N/A     |  N/A  |          No           | Black |          No          |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
21722343 | Yes |   No   | Grey  |    Valid    | Grey  |      No        | Invisible  |    N/A     |  N/A  |          No           | Black |          No          |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
48960650 | Yes |  Yes   | Grey  |   Invalid   | Black |      No        | Invisible  |    N/A     |  N/A  |          No           | Black |          No          |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
5805194  | Yes |  Yes   | Grey  |    Valid    | Black |      No        |  Visible   |    Yes     | Black |          No           | Black |          No          |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
50840409 | Yes |  Yes   | Grey  |    Valid    | Black |      Yes       |  Visible   |    Yes     | Grey  |          No           | Black |          No          |

基于Albireo的响应,该版本不使用jQuery,CSS的特异性更好。

const triggerEvent=(el,eventName)=>{let event=document.createEvent('HTMLEvents')event.initEvent(eventName,true,false)el.dispatchEvent(事件)}let select=document.querySelector('.placeholder select')select.addEventListener('change',(e)=>{e.target.classList[e.target.value==0?'add':'remove']('empty')})triggerEvent(选择,“更改”)占位符选择选项{颜色:#000000;}占位符选择选项:第一个子项{颜色:#444444;字体样式:斜体;字号:粗体;}.占位符-选择为空{颜色:#7F7F7F;}<select class=“placeholder select”><option value=“0”selected=“selected”>选择</选项><option value=“1”>有些东西</option><option value=“2”>其他内容</option><option value=“3”>另一个选项</option></选择>

使用类名包,这里有一个与我的React功能组件一起工作的解决方案。我的组件使用钩子,但这可能对解决方案并不重要。这种方法是基于类的解决方案的一种功能性模仿。。。https://www.derpturkey.com/select-placeholder-with-react/

组件JS。。。

function NavBar(props, prevProps) {
            const ClassNames = require("classnames");  // package needs require rather than import
            const [where, changeWhere] = useState("");  // my component's value
            // classnames will add placeholderSelect class if chosen option's value is empty
            let whereClass = ClassNames("myOtherStyleRules", {
                placeholderSelect: !where,
            });
            ...
            return (
            ...
            <div id="where">
                            <select
                              className={whereClass}
                              value={where}
                              ...
                            >
                              <option value="" hidden> where? </option>    //  value must be empty, hidden from choice
                              <option value="24">Anchorage</option>
                              <option value="27">Birmingham</option>
                              <option value="28">Detroit</option>
                              <option value="25">Los Angeles</option>
                              <option value="26">Oahu</option>
                              <option value="29">Seattle</option>
                            </select>
                ... 

组件CSS。。。

        .placeholderSelect {
          color: rgb(167, 167, 167);
        }