为什么这个正则表达式断言不匹配? [英] Why this regex assertion doesn't match?

问题描述

我正在尝试在 html 标签之间预存内容，我正在尝试这个简单的断言模式，但我不明白为什么它不匹配这个字符串.

I'm trying to just preg content between html tags, I'm trying this simple assertion pattern and I don't understand why it doesn't match this string.

<a href=http://url.com title="link">this is a ling</a>

(?<=<a.*>)([ w]*)(?=<.*/a>)

Debuggex 演示

推荐答案

Lookbehinds on debuggex(PCRE、Javascript 和 Python)不能是可变宽度的，这意味着您可以使用 (?<=<a>) 具有固定宽度(3 个字符)但长度不能变化 (?<=<a.*>)(可以有 3 个字符，或 4 个字符)，或 5 等).

Lookbehinds on debuggex (PCRE, Javascript and Python) cannot be of variable width, meaning that you can use (?<=<a>) which has a fixed width (3 characters) but not something that can vary in length (?<=<a.*>) (can have 3 characters, or 4, or 5, etc).

正则表达式根本无效，但 debuggex 告诉您没有匹配项.

The regex simply is not valid but debuggex tells you that there is no match.

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