匹配以特殊字符开头或结尾的整个单词 [英] Matching whole words that start or end with special characters

问题描述

我需要JavaScript中的正则表达式来匹配以特殊字符开头或结尾的整个单词吗?

I need a regular expression in javascript that matches whole words that start or end with special characters?

这本来应该很容易，但是由于某些原因，?之后的\b并没有达到我的预期:

It was supposed to be easy, but for some reason \b after ? doesn't behave as I expected:

> /FOO\?/.exec('FOO? ')
[ 'FOO?', index: 0, input: 'FOO? ', groups: undefined ]
> /FOO\?\b/.exec('FOO? ')
null

我需要什么，例如，如果我的单词是"FOO"? (包括问号)，我要匹配:

What I need, for instance if my word is "FOO?" (including the question mark), I want to match:

"FOO?很酷"，您认为FOO吗?"

"FOO? is cool", "do you think that FOO??"

但不是:"FOO很酷"，"FOO?很酷"，"aaFOO?很酷"

but not: "FOO is cool", "FOO?is cool", "aaFOO?is cool"

它也适用于以?"开头的单词.例如，如果我的单词为?FOO"，我想匹配:

It should also work for words that start with "?". For instance, if my word if "?FOO", I want to match:

?FOO很酷"，我爱?FOO"

"?FOO is cool", "I love ?FOO"

但不是:"FOO很酷"，"FOO?很酷"，"aaFOO?很酷"

but not: "FOO is cool", "FOO?is cool", "aaFOO?is cool"

我希望这是有道理的.

推荐答案

\b单词边界构造是不明确的.您需要使用明确的结构，以确保匹配的单词的左/右有非单词字符或字符串的开始/结尾.

The \b word boundary construct is ambiguous. You need to use unambiguous constructs that will make sure there are non-word chars or start/end of string to the left/right of the word matched.

您可以使用

/(?:^|\W)\?FOO\?(?!\w)/g

在这里，(?:^|\W)是一个非捕获组，它与字符串的开头或任何非单词char，ASCII字母，数字和_以外的char匹配. (?!\w)是否定的超前查询，如果在当前位置的右边立即有一个单词char，则匹配失败.

Here, (?:^|\W) is a non-capturing group that matches either the start of a string or any non-word char, a char other than an ASCII letter, digit and _. (?!\w) is a negative lookahead that fails the match if, immediately to the right of the current location, there is a word char.

或者，在与ECMAScript 2018兼容的JS环境中，

Or, with ECMAScript 2018 compatible JS environments,

/(?<!\w)\?FOO\?(?!\w)/g

请参见此regex演示.

(?<!\w)是一个向后查找的否定字符，如果当前位置左侧紧接着有一个字符char，则匹配失败.

The (?<!\w) is a negative lookbehind that fails the match if there is a word char immediately to the left of the current location.

在代码中，您可以将其直接与String#match一起使用以提取所有出现的内容，例如s.match(/(?<!\w)\?FOO\?(?!\w)/g).

In code, you may use it directly with String#match to extract all occurrences, like s.match(/(?<!\w)\?FOO\?(?!\w)/g).

第一个表达式需要一个围绕您要提取的单词的捕获组:

The first expression needs a capturing group around the word you need to extract:

var strs = ["?FOO is cool", "I love ?FOO", "FOO is cool", "FOO?is cool", "aaFOO?is cool"];
var rx = /(?:^|\W)(\?FOO)(?!\w)/g;
for (var s of strs) {
  var res = [], m;
  while (m=rx.exec(s)) {
    res.push(m[1]);
  }
  console.log(s, "=>", res);
}

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