December 2017
Intermediate to advanced
329 pages
6h 9m
Chinese
Content preview from React学习手册
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Props
、
State
和组件树
｜
117
new Error("A title must be a string") :
(props[propName].length > 20) ?
new Error(`title is over 20 characters`) :
null
}
所有属性类型验证器都是函数。为了实现自定义属性验证函数，我们将会对
propTypes
对象下的
title
属性和一个回调函数关联。当渲染该组件时，
React
将会把属
性对象和当前属性作为参数传递给该函数。
我们可以使用这些参数对特定属性的属性
值进行校验。
在这种情况下，我们首先需要确保
title
是字符串类型。如果
title
不是字符串，那么
验证器将会返回一个包含错误提示的信息：“
A title must be a string
”。如果
title
是
字符串类型，那么就会检查它的值是否超过了
20
个字符。如果
title
的值在
20
个字符
以内，验证器函数将会返回
null
值。如果
title
的值大于
20
个字符，那么验证器函数将
会返回一个错误。
React
将会捕获该错误信息，然后以警告的形式在控制台上输出。
自定义验证器允许用户实现特定的验证规则。一个自定义验证器可以执行多重验证，
只在不符合某些特定规则时返回错误。在使用或者复用用户组件时，采用自定义验证
器是一种是防止产生错误的好办法。
ES6
类和无状态函数式组件
在前面章节中，我们已经知道属性验证功能，以及使用
React.createClass
创建自定
义组件时，可以添加默认的属性值。 ...
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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.