CSS伪级：基于其输入的样式表单字段

<code class="language-html"><img src="/static/imghwm/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/173993023124148.jpg" class="lazy" alt="CSS Pseudo-classes: Styling Form Fields Based on Their Input ">

**Key Concepts: Styling Form Fields with CSS Pseudo-Classes**

This article explores CSS pseudo-classes specifically designed for styling form fields based on user input, field requirements, and enabled/disabled states.  We'll cover how to leverage these selectors to enhance user experience and provide clear visual feedback.

<img src="/static/imghwm/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/173993023288237.jpg" class="lazy" alt="CSS Pseudo-classes: Styling Form Fields Based on Their Input ">

*This section is adapted from "CSS Master" by Tiffany B. Brown.*

Let's examine CSS pseudo-classes tailored for form fields and their inputs. These selectors enable styling based on input validity, required fields, and enabled/disabled status.  These pseudo-classes are inherently form-specific, reducing the need for extensive scoping. However, targeted selectors remain beneficial for differentiating styling across various form control types.

**`:enabled` and `:disabled`**

These pseudo-classes target elements with or without the `disabled` HTML5 attribute. This applies to input controls (e.g., `<input>`, `<select>`, `<button>`), and `<fieldset>` elements.  Form elements are enabled by default; the `disabled` attribute toggles this state.  `:enabled` selects elements lacking the `disabled` attribute, while `:disabled` selects elements possessing it.

```css
button:disabled {
    opacity: 0.5;
}</fieldset></button></select></code>

:required和:optional

>

这些伪级反映了属性的存在或不存在。 浏览器通常仅表示表单提交时所需的字段。 required允许预次访问视觉提示。 :required

<code class="language-css">input:required {
    border: 1px solid #ffc107;
}</code>

的工作方式相似，选择没有> :optional required

<code class="language-css">select:optional {
    border: 1px solid #ccc;
}</code>

:checked此伪级仅适用于无线电按钮和复选框，所选输入的样式。 自定义样式通常需要巧妙的选择器组合（同级组合，伪元素），因此浏览器不一致。>

<code class="language-css">[type=radio]:checked + label {
    font-weight: bold;
    font-size: 1.1rem;
}</code>

和

:in-range> :out-of-range这些伪级可与>，

和

>输入一起工作，需要和/或<range></range>属性。 <number></number> <date></date>min max

<code class="language-css">:out-of-range {
    background: #ffeb3b;
}

:in-range {
    background: #fff;
}</code>

和

> 这些伪级样式基于输入有效性（类型，模式，最小/最大）。 :valid:invalid

多个状态和链接

表格控件可以同时具有多个状态。 管理特异性和级联冲突可能需要仔细考虑或限制伪级使用。 伪级可以被束缚（例如，

）。

> （脚注6）：在html5中，

属性的存在，无论其价值如何，都表示所需的字段。>

input:focus:invalid常见问题（常见问题解答）：

（为简短而省略了此部分，因为它是原始FAQ部分的直接重复。）

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