javascript - 为什么下划线(_)不被视为非单词字符？

Question

为什么下划线(_)不被视为非单词字符？此正则表达式\W 匹配所有非单词字符但不匹配下划线。

Answer 1

引用 Jeffrey Friedl 关于正则表达式的书，这最初是对 Perl 正则表达式的更改。根据允许命名 Perl 变量的字符，回到 1988 年 [第 89 页]:

Perl 2 was released in June 1988. Larry had replaced the regex code entirely, this time using a greatly enhanced version of the Henry Spencer package mentioned in the previous section. You could still have at most nine sets of parentheses, but now you could use | inside them. Support for \d and \s was added, and support for \w was changed to include an underscore, since then it would match what characters were allowed in a Perl variable name.