[翻译]High Performance JavaScript(017)
A Note on Benchmarking 测试基准说明
Because a regex's performance can be wildly different depending on the text it's applied to, there's no straightforward way to benchmark regexes against each other. For the best result, you need to benchmark your regexes on test strings of varying lengths that match, don't match, and nearly match.
因为正则表达式性能因应用文本不同而产生很大差异，没有简单明了的方法可以测试正则表达式之间的性能差别。为得到最好的结果，你需要在各种字符串上测试你的正则表达式，包括不同长度，能够匹配的，不能匹配的，和近似匹配的。
That's one reason for this chapter's lengthy backtracking coverage. Without a firm understanding of backtracking, you won't be able to anticipate and identify backtracking-related problems. To help you catch runaway backtracking early, always test your regexes with long strings that contain partial matches. Think about the kinds of strings that your regexes will nearly but not quite match, and include those in your tests.
这也是本章长篇大论回溯的原因之一。如果没有确切理解回溯，就无法预测和确定回溯相关问题。为帮助你早日把握回溯失控，总是用包含特殊匹配的长字符串测试你的正则表达式。针对你的正则表达式构思一些近似但不能完全匹配的字符串，将他们应用在你的测试中。
More Ways to Improve Regular Expression Efficiency 提高正则表达式效率的更多方法
The following are a variety of additional regex efficiency techniques. Several of the points here have already been touched upon during the backtracking discussion.
下面是一写提高正则表达式效率的技术。几个技术点已经在回溯部分讨论过了。
Focus on failing faster
关注如何让匹配更快失败
Slow regex processing is usually caused by slow failure rather than slow matching. This is compounded by the fact that if you're using a regex to match small parts of a large string, the regex will fail at many more positions than it will succeed. A change that makes a r
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——返回一个用来表示表达式的数据类型的字符串
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Regular Expression Optimization 正则表达式优化
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