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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442
｜
第
16
章
图
16
-
7
：使用 File API 读取一个图像
16.10
使用
Web
组件扩展可能性
16.10.1
问题
你需要把特定的外观和行为封装到一个组件中，像普通的
HTML
元素那样使用，但
是不想使用
Web
框架。
16.10.2
方案
考虑使用
Web
组件自定义可重用的
HTML
元素。
Web
组件包括模板、自定义元素
和
Shadow DOM
。详细讨论如下。
16.10.3
讨论
Web
组件有点像自成一体的网页小部件（
widget
），当然这只是一种浅层理解。
Web
组件这个术语可指代几种不同的结构。下面几节分别介绍这几种结构，并提供
示例、讨论腻子脚本及展望未来。
编写
Web
应用
｜
443
HTML
模板
template
元素现已纳入
HTML5
规范。目前，多数现代浏览器都支持（
https://oreil.
ly/SJZDC
）。
template
元素中是打包成一个整体的
HTML
，直到克隆时才实例化。
template
元素在加载时解析，目的是确保内容有效，但还不存在。
模板用起来十分符合直觉。以当下单页
JavaScript
应用经常执行的一项操作为例：
以无序列表（
ul
，或者段落或表格等）的形式显示从
Web
服务中获取的数据。以往，
我们需要使用
DOM
方法查询现有的
ul
元素，然后创建各个列表项目（
li
），把文
本添加到列表项目中，最后再把列表项目添加到无序列表中。 ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
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.