正则表达式末尾大括号中逗号分隔的数字是什么意思? [英] What do comma separated numbers in curly braces at the end of a regex mean?

问题描述

我试图理解以下正则表达式，我理解最初的部分，但我无法弄清楚 {3,19} 在这里做什么:

I am trying to understand the following regex, I understand the initial part but I'm not able to figure out what {3,19} is doing here:

/[A-Z][A-Za-z0-9\s]{3,19}$/

推荐答案

这就是称为量词的自定义重复操作.

That is the custom repetition operation known as the Quantifier.

\d{3} 将正好找到三位数字.

\d{3} will find exactly three digits.

[a-c]{1,3} 将查找 a、b 或 c 至少出现一次，但最多出现 3 次.

[a-c]{1,3} will find any occurrance of a, b, or c at least one time, but up to three times.

\w{0,1} 表示可以选择找到一个单词字符.这与放置问号相同，例如:\w?

\w{0,1} means a word character will be optionally found. This is the same as placing a Question Mark, e.g.: \w?

(\d\w){1,} 将找到一个数字后跟一个单词字符的任意组合至少一次，但最多无限次.所以它会匹配 1k1k2k4k1k5j2j9k4h1k5k 这与加号相同，例如:(\d\w)+

(\d\w){1,} will find any combination of a Digit followed by a Word Character at least One time, but up to infinite times. So it would match 1k1k2k4k1k5j2j9k4h1k5k This is the same as a Plus symbol, e.g.: (\d\w)+

b{0,}\d 将可选地找到字母 b 后跟一个数字，但也可以匹配无限字母 b's 后跟一个数字.所以它会匹配5、b5，甚至bbbbbb5.这与星号相同.例如:b*\d

b{0,}\d will optionally find the letter b followed by a digit, but could also match infinite letter b's followed by a digit. So it will match 5, b5, or even bbbbbbb5. This is the same as an Asterisk. e.g.: b*\d

量词

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