December 2017
Intermediate to advanced
329 pages
6h 9m
Chinese
Content preview from React学习手册
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22
｜
第
2
章
<script
src="https://cdnjs.cloudflare.com/ajax/libs/babel-core/5.8.23/browser.js">
</script>
<script src="script.js" type="text/babel">
</script>
浏览器中的转译
这种方法意味着浏览器会在运行时执行转译工作。这对于上线的产品来说并非
良策，因为它会大大拖慢页面应用的响应速度。第
5
章将会向读者详细介绍如
何在已经上线的产品中解决这个问题。现在，
CDN
服务将会允许客户端发现和
使用
ES6
的特性。
你心里也许会这么想：“太棒了！当所有浏览器都支持
ES6
时，我们就不需要再使用
Babel
了！”不过，就目前来看，如果我们希望使用下一版本的特性还离不开
Babel
。
除非发生革命性的变化，在可预见的将来我们可能还需要使用
Babel
转译代码。
ES6
的对象和数组
ES6
规范为我们提供了一种使用对象和数组的新方法，并且可以在这些数据集中限定
变量作用域的范围。这些特性包括解构，对象语义增强和扩展运算符。
解构赋值
解构赋值允许用户将某个对象内的字段的作用域本地化，并且可以声明哪些值是将要
使用的。
以对象
sandwich
为例。它包含四个字段，但是我们只想使用其中两个字段的值。那么
我们可以将其中的
bread
和
meat
属性的作用域本地化：
var sandwich = {
bread: "dutch crunch",
meat: "tuna",
cheese:
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
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.