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摘要

:required CSS 伪类 表示 任意 <input> 元素表示任意拥有required属性的 <input> 或 <textarea> 元素使用它. 它允许表单在提交之前容易的展示必填字段并且渲染其外观. 

:optional伪类可用于表单可选元素提供外观.

语法

:required

例子

查看示例 :invalid .

规范

Specification Status Comment
HTML Living Standard
:required
Living Standard No change.
HTML5
:required
Recommendation Defines the semantic regarding HTML and constraint validation.
Selectors Level 4
:required
Working Draft No change.
CSS Basic User Interface Module Level 3
:required
Recommendation Defines the pseudo-class, but not the associated semantic.

浏览器兼容

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 10.0 4.0 (2) 10 10.0 5.0
Feature Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support ? 4.0 (2) 未实现 10.0 5.0

参见

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