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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262
第
10
章
错误和测试
代码错误不可避免。通常，错误是可以预期的。与外部资源（例如文件、数据库或
Web
服务器
API
）交互的操作往往存在风险。从代码外部获取的信息，不管是从网
页表单中读取，还是从其他库接收，都有可能存在错误，或者不同于预期的形式。
但是，老话说得好，错误不可怕，就看你如何处理错误。
那么，我们应该怎么处理错误呢？
JavaScript
的默认行为是在出错的位置崩溃，悄
无声息地向控制台输出堆栈跟踪。不过，也有更好的处理方式。你可以捕获错误，
做出反应，也可以修改之后再次抛出，如果你愿意，甚至可以置之不理。与很多其
他语言相比，
JavaScript
的错误处理功能相对简陋。但是，基本的错误处理功能还是
很重要的，本章的很多经典实例就专注这个任务。
防御错误是肯定要做的，不过避免错误发生同样重要。在这方面，有很多支持
JavaScript
的测试框架，包括
Jest
、
Mocha
、
Jasmine
和
Karma
。你可以借助这些框
架编写单元测试，确保代码能按预期执行。本章将简要介绍
Jest
。
10.1
捕获并压制错误
10.1.1
问题
你执行的任务可能失败，你不想让错误中断代码，也不希望错误出现在开发者控制
台中。
错误和测试
｜
263
10.1.2
方案
把可能失败的代码放在
try...catch
块中，如下所示。 ...
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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.