June 2021
Intermediate to advanced
290 pages
9h 21m
Chinese
Content preview from Node与Express开发（第2版）
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14
｜
第
2
章
2.5.2
事件驱动编程
Node
背后的核心哲学就是
事件驱动编程
。对你（程序员）就意味着，必须要知悉有什么
事件可能会发生以及如何响应。很多人是通过实现用户界面才第一次认识事件驱动编程
的：用户点击了某个东西，然后你处理一个
点击事件
。事件驱动编程是很好的比喻，因为
很显然程序员没法控制用户是否点击以及何时点击一个东西，因此，事件驱动编程是非常
直观的。把这个概念推广到服务器上，会略微有些难以理解，但基本原理一样。
在前面的示例代码中，事件是隐含的：正在处理的事件就是一个
HTTP
请
求。
http.
createServer
方法需要一个函数作为参数，每次创建新的
HTTP
请求时，就会调用这个函
数。简单示例只是把内容类型设置为普通文本，然后发送字符串“
Hello world!
”。
一旦你开始从事件驱动编程的角度思考，就会发现到处都是事件。用户使用你的应用时，
从一页导航到另一页，或从一块内容导航到另一块内容，就是一个事件。你的应用如何响
应这样的导航事件，就叫作
路由
。
2.5.3
路由
路由指的是对客户端内容请求的满足机制。对基于
Web
的客户端
/
服务器端应用，客户端
在
URL
中指
定了想要的内容，具体来讲就是
URL
中的路径和查询串（第
6
章将更详细地
讨论
URL
的各个部分）
。
通常，服务器端的路由依赖于路径和查询串，但还有别的信息可以使用：
HTTP
头、
域名、
IP
地址，等等。这使得服务器端可以把更多的因素纳入考
虑，例如用户的大概位置，或是用户首选的语言。
下面对前面的“
Hello world!
”做一下扩展，让它做点儿更有意思的事情。做一个只包含主 ...
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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.
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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.