在正则表达式中设置最小和最大字符？ [英] Set min and max characters in a regular expression?

问题描述

我写了一个正则表达式，它匹配任意数量的字母，这些字母之间有任意数量的单个空格。我希望这个正则表达式也强制执行最小和最大字符数，但我不知道该怎么做（或者如果可能的话）。

I've written a regular expression that matches any number of letters with any number of single spaces between the letters. I would like that regular expression to also enforce a min and max number of characters, but I'm not sure how to do that (or if it's possible).

My正则表达式为：

[A-Za-z](\s?[A-Za-z])+

我意识到它只匹配一个空格周围的两组字母，所以我稍微修改了它来修复那。最初的问题仍然是相同的。

I realized it was only matching two sets of letters surrounding a single space, so I modified it slightly to fix that. The original question is still the same though.

有没有办法强制执行至少三个字符，最多三个字符？

Is there a way to enforce a minimum of three characters and a maximum of 30?

推荐答案

是

就像 + 意味着一个或者更多你可以使用 {3,30} 匹配3到30之间

Just like + means one or more you can use {3,30} to match between 3 and 30

例如 [az] {3,30} 匹配3到30个小写字母

For example [a-z]{3,30} matches between 3 and 30 lowercase alphabet letters

来自模式类的文档

X{n,m}    X, at least n but not more than m times

在您的情况下，匹配3-30个字母后跟空格可以通过以下方式完成：

In your case, matching 3-30 letters followed by spaces could be accomplished with:

([a-zA-Z]\s){3,30}

如果你需要尾随空格，如果你不需要，你可以使用：（2-29次字母+空格，然后是字母）

If you require trailing whitespace, if you don't you can use: (2-29 times letter+space, then letter)

([a-zA-Z]\s){2,29}[a-zA-Z]

如果您想要将空格数作为字符，则需要将该数字除以2以获得

If you'd like whitespaces to count as characters you need to divide that number by 2 to get

([a-zA-Z]\s){1,14}[a-zA-Z]

如果尾部空格是可选的，您可以将 \s？添加到最后一个。这些都在 RegexPlanet 上进行了测试

You can add \s? to that last one if the trailing whitespace is optional. These were all tested on RegexPlanet

如果您希望整个字符串总共在3到30个字符之间，您可以使用前瞻性添加（？= ^。{3,30} $） RegExp并删除其他大小限制

If you'd like the entire string altogether to be between 3 and 30 characters you can use lookaheads adding (?=^.{3,30}$) at the beginning of the RegExp and removing the other size limitations

所有这一切，老实说我可能只是测试 String 是 .length 属性。它更具可读性。

All that said, in all honestly I'd probably just test the String's .length property. It's more readable.

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