正则表达式否定：处理条件 if 语句，如果满足则取消匹配答案

【问题标题】：Regex Negation: Handling conditional if statements that cancel the match if fulfilled正则表达式否定：处理条件 if 语句，如果满足则取消匹配
【发布时间】：2021-01-26 23:48:06
【问题描述】：

比如说我有这样的文字：

hello world **ant*** lorem **cat** opposum** *** ***antelope*** *rabbit __dog__

我想匹配只有 ** 和 __ 作为其前面和结束字符的字符串。所以在上面的例子中，我只想匹配“cat”和“dog”。这意味着如果周围有多余的字符，我必须取消或否定匹配。例如，***dog** 或 __dog___ 应该会失败。

我试图用消极的目光环顾 http://www.regular-expressions.info/lookaround.html 来解决这个问题，但无济于事。

这是我目前的模式

const pattern = /([^*])\*(\w+)\*([^*])/g;
const match = pattern.exec(text);
const annotatedText = match[0];
const matchedText = match[1];

// Return if annotatedText is a possible match for bolditalic
if (annotatedText.startsWith("***") || annotatedText.startsWith("___")) {
        return;
}
// Return if the matchedText has spaces in between
if (/\s/.test(matchedText)) {
        return;
}
if (text.match(/^([*_ \n]+)$/g)) {
        return;
}

在 javascript 正则表达式中，

基本上，我想删除 javascript 字符串检查并在正则表达式模式本身上添加逻辑。

【问题讨论】：

标签： regex regex-lookarounds regex-negation

【解决方案1】：

使用

/(?<=(?<!\*)\*\*)\w+(?=\*\*(?!\*))|(?<=(?<!_)__)\w+(?=__(?!_))/gi

见proof。

说明

--------------------------------------------------------------------------------
  (?<=                     look behind to see if there is:
--------------------------------------------------------------------------------
    (?<!                     look behind to see if there is not:
--------------------------------------------------------------------------------
      \*                       '*'
--------------------------------------------------------------------------------
    )                        end of look-behind
--------------------------------------------------------------------------------
    \*                       '*'
--------------------------------------------------------------------------------
    \*                       '*'
--------------------------------------------------------------------------------
  )                        end of look-behind
--------------------------------------------------------------------------------
  \w+                      word characters (a-z, A-Z, 0-9, _) (1 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  (?=                      look ahead to see if there is:
--------------------------------------------------------------------------------
    \*                       '*'
--------------------------------------------------------------------------------
    \*                       '*'
--------------------------------------------------------------------------------
    (?!                      look ahead to see if there is not:
--------------------------------------------------------------------------------
      \*                       '*'
--------------------------------------------------------------------------------
    )                        end of look-ahead
--------------------------------------------------------------------------------
  )                        end of look-ahead
--------------------------------------------------------------------------------
 |                        OR
--------------------------------------------------------------------------------
  (?<=                     look behind to see if there is:
--------------------------------------------------------------------------------
    (?<!                     look behind to see if there is not:
--------------------------------------------------------------------------------
      _                        '_'
--------------------------------------------------------------------------------
    )                        end of look-behind
--------------------------------------------------------------------------------
    __                       '__'
--------------------------------------------------------------------------------
  )                        end of look-behind
--------------------------------------------------------------------------------
  \w+                      word characters (a-z, A-Z, 0-9, _) (1 or
                           more times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  (?=                      look ahead to see if there is:
--------------------------------------------------------------------------------
    __                       '__'
--------------------------------------------------------------------------------
    (?!                      look ahead to see if there is not:
--------------------------------------------------------------------------------
      _                        '_'
--------------------------------------------------------------------------------
    )                        end of look-ahead
--------------------------------------------------------------------------------
  )                        end of look-ahead

JavaScript 代码：

const string = 'hello world **ant*** lorem **cat** opposum** *** ***antelope*** *rabbit __dog__';
console.log(string.match(/(?<=(?<!\*)\*\*)\w+(?=\*\*(?!\*))|(?<=(?<!_)__)\w+(?=__(?!_))/gi))

【讨论】：

您好，感谢您的回答！我已经对其进行了测试，并且匹配效果很好。一个警告：是否有可能同时捕捉到后面和后面的字符？例如：hello world **dog** 应该返回 **dog** 而不是 dog
@wolfgang 更简单：(?<!\*)\*\*\w+\*\*(?!\*)|(?<!_)__\w+__(?!_)。见proof。如果对您有用，请考虑接受/支持。
完美！非常感谢，我会将此设置为正确的解决方案。