If Else 正则表达式匹配 [英] If Else regex matching

问题描述

我想构建一个正则表达式，在其中搜索包含连续 12 位数字的字符串.如果没有匹配项，请查找一行中只有 10 位数字的字符串.

例如:

a123456789012aa1234567890a

会回来:

123456789012

如果输入是:

a1234aa1234567890a

它会返回:

1234567890

我设法为各个操作创建了正则表达式，将 (?<!\d)\d{10}(?!\d) 输入 10 位数字和 (?<!\d)\d{12}(?!\d) 用于 12 位数字，但我无法以 if-else 样式将它们分组.

我尝试了以下方法:

(?(?

但如果第一个模式不匹配，则正则表达式不会尝试匹配第二个模式，不返回任何内容

解决方案

你可以像这样使用一个简单的正则表达式:

\d{12}|\d{10}

情况 2:

顺便说一句，如果您想捕获内容，请使用捕获组:

(\d{12}|\d{10})

I want to build a regex where it searches for a string containing 12 digits in a row. If there's no match, look for a string with only 10 digits in a row.

For example:

a123456789012a
a1234567890a

Would return:

123456789012

And if the input is:

a1234a
a1234567890a

It would return:

1234567890

I managed to create the regex for the individual operations, beeing (?<!\d)\d{10}(?!\d) for 10 digits and (?<!\d)\d{12}(?!\d) for 12 digits, but I can't group them up in a if-else style.

I tried the following:

(?(?<!\d)\d{12}(?!\d)|((?<!\d)\d{10}(?!\d)))

but if the first pattern don't match, the regex don't try to match the second, returning nothing

解决方案

You can use a simple regex like this:

\d{12}|\d{10}

working demo

Look that I have not used multiline nor global flags. This way the pattern is going to find the first match you want.

Case 1:

Case 2:

BTW, use capturing groups if you want to capture the content:

(\d{12}|\d{10})

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