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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518
｜
第
19
章
console.log('Running a job at midnight ');
}, {
scheduled:
true
,
timezone: "America/New_York"
});
scheduled
选项的值是一个布尔值，默认为
true
。如果设为
false
，则不运行定期
作业。
timezone
选项为日程指定时区。如果想查看全部时区名称，请访问
Moment.
js
的时区页面（
https://oreil.ly/VhAkl
）。
19.9
测试
WebSockets
应用的性能和功能
19.9.1
问题
你有一个应用频繁向连接的每个客户端发送更新信息，你担心应用的性能和负载。
19.9.2
方案
做速度（性能）测试和负载测试。详见下一节的讨论。
19.9.3
讨论
得益于
Node
和
WebSockets
，以及其他双向通信技术，在网页中不再需要使用计时
器访问服务器获取新数据，服务器可以直接把新数据推送给连接的所有客户端。例
程
17-4
演示的动画效果滚动时间线就是这种应用。
但是，问题也随之浮现：是的，效果很酷，但是这背后的代价呢？如果有
10
（
100
、
1000
或
10000
）个客户端连接，服务器会不会崩溃呢？所有客户端都能得到相同的
响应吗？两种测试可以回答这些问题。
•
速度（性能）测试：测试页面的加载速度，尤其是服务器承受一定压力时。
•
负载测试：模拟多个客户端同时访问页面。
有提供这两种测试的服务，如果是大型商业运营公司，对应用的可靠性和性能极为
管理
Node
｜
519
看重，强烈建议你使用这类服务。有些服务，例如 ...
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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.