September 2022
Intermediate to advanced
585 pages
8h 17m
Chinese
Content preview from JavaScript 经典实例：第三版
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处理
HTML
｜
341
另外，你还要考虑到
JavaScript
被禁用的情况，在服务器端为表单提供同等的反馈，
然后在单独的页面中呈现结果。
此外，必填的表单字段也要提前标记出来。在表单字段的标注中添加一个星号，并
指出带星号的表单字段是必填项。使用
aria-required
属性确保必填要求可被使用
辅助设备的用户知晓。使用
aria-required
时，还建议使用
HTML5 required
属性，
启用浏览器原生验证。
12.17.4
参考
12.16
节介绍了简化表单验证的库和模块，还提到了
HTML5
表单验证技术。
12.18
保障自动更新区域的无障碍功能
12.18.1
问题
网页中有一个区域定期更新，例如列出最近更新文件的区域，或者展示某一话题最
新推文的区域。你想确保页面更新后，使用屏幕阅读器的人知道出现了新信息。
12.18.2
方案
为有更新的元素设置
WAI-ARIA
区域属性。
<div
id="update" role="log" aria-live="polite" aria-atomic="true"
aria-relevant="additions"
>
</div>
12.18.3
讨论
网页加载后，无须用户干预即可更新的区域，在
WAI-ARIA
中叫作
Live Regions
。
这算得上是最容易实现的
ARIA
功能，主动提供即时结果。而且，除了更新页面所
需的
JavaScript
之外，不涉及任何代码。
342
｜
第
12
章
<div
id="update" role="log" aria-live="polite" ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.