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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291
第
11
章
浏览器工具
作为一名
Web
开发人员，浏览器是世人访问我们作品的窗口。浏览器还为网站的
开发和测试提供了很多有用的工具。我们应该投入时间和精力学习如何使用浏览器
的开发工具，以便在调试代码时事半功倍。本章介绍一些助力调试、剖析和分析
JavaScript
代码的功能。
简单起见，本章的所有示例都使用
Google Chrome
浏览器的开发者工具（
DevTools
）。
写作本书时，全球浏览器市场份额中，
Chrome
占比超过
65%
（
https://oreil.ly/
QFZD9
）。多数其他浏览器也有类似的功能，比如
Mozilla
的
Firefox
开发者版（
https://
oreil.ly/lJSel
）就是不错的替代选择，也为开发者提供了丰富的功能。
11.1
调试
JavaScript
11.1.1
问题
你想知道在执行
JavaScript
代码的特定时刻某个变量的值。
11.1.2
方案
使用断点（
breakpoint
）检查代码的值和类型。设定断点后，浏览器的调试器在断点
处停止执行代码，显示当前作用域中的各个值。然后，可以逐步向前执行
JavaScript
代码，或者一直执行到最后。图
11-1
是代码在一个断点处暂停时的截图。
292
｜
第
11
章
图
11
-
1
：设定了一个断点的 Chrome 调试器截图
在
Chrome ...
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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.