[a-zA-Z0-9_] 中的 _ 是什么意思? [英] What does the _ in [a-zA-Z0-9_] mean?

问题描述

以下正则表达式中的下划线是什么意思?

What does the underscore mean in the following regex?

[a-zA-Z0-9_]

_ 似乎没什么区别，所以我不明白它的用途.

The _ seems to make no difference so I don't understand the purpose of it.

推荐答案

表示除小写字母、大写字母和数字外，还要匹配下划线字符.

It means to match the underscore character in addition to lowercase letters, uppercase letters, and numbers.

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