Javascript Regex Word Boundary带有可选的非单词字符 [英] Javascript Regex Word Boundary with optional non-word character

问题描述

我希望在字符串中找到关键字匹配。我试图使用单词边界，但这可能不是该解决方案的最佳情况。关键字可以是任何单词，并且可以在前面加上非单词字符。字符串可以是任何字符串，并且可以包含数组中的所有这三个字，但我只应匹配关键字：

I am looking to find a keyword match in a string. I am trying to use word boundary, but this may not be the best case for that solution. The keyword could be any word, and could be preceded with a non-word character. The string could be any string at all and could include all three of these words in the array, but I should only match on the keyword:

['hello', '#hello', '@hello'];

这是我的代码，其中包含在 post ：

Here is my code, which includes an attempt found in post:

let userStr = 'why hello there, or should I say #hello there?';

let keyword = '#hello';

let re = new RegExp(`/(#\b${userStr})\b/`);

re.exec(keyword);

• 如果字符串始终以＃开头，那就太好了，但是没有。


• 然后我尝试了这个 /（＃？\ b $ {userStr}）\ b / ，但是如果该字符串以＃开头，它尝试匹配 ## hello 。


• matchThis str可以是数组中的3个示例中的任何一个，userStr可能包含 matchThis 但只有一个是准确的


• This would be great if the string always started with #, but it does not.
• I then tried this /(#?\b${userStr})\b/, but if the string does start with #, it tries to match ##hello.
• The matchThis str could be any of the 3 examples in the array, and the userStr may contain several variations of the matchThis but only one will be exact

推荐答案

你需要在这里说明3件事：

You need to account for 3 things here:



• 重点是 \b 字边界是一个上下文 - 依赖构造，如果你的输入不总是只有字母数字，你需要明确的单词边界


• 你需要在构造函数RegExp表示法中双重转义特殊字符


• 当你将变量传递给正则表达式时，你需要确保所有特殊字符都被正确转义。


• The main point is that a \b word boundary is a context-dependent construct, and if your input is not always alphanumeric-only, you need unambiguous word boundaries
• You need to double escape special chars inside constructor RegExp notation
• As you pass a variable to a regex, you need to make sure all special chars are properly escaped.

使用

let userStr = 'why hello there, or should I say #hello there?';
let keyword = '#hello';
let re_pattern = `(?:^|\\W)(${keyword.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&')})(?!\\w)`;
let res = [], m;

// To find a single (first) match
console.log((m=new RegExp(re_pattern).exec(userStr)) ? m[1] : "");

// To find multiple matches:
let rx = new RegExp(re_pattern, "g");
while (m=rx.exec(userStr)) {
    res.push(m[1]);
}
console.log(res);

模式说明



• （？：^ | \\ W） - 匹配字符串开头或任何非单词字符的非捕获字符串


• （$ {keyword.replace（/ [ - \ / \ \ ^ $ * +？。（）| [\] {}] / g，'\\ $&'）}） - 第1组：关键字带有转义特殊字符的值


• （？！\\\\） - 如果匹配失败则为负面预测当前位置右侧有一个字词char。


• (?:^|\\W) - a non-capturing string matching the start of string or any non-word char
• (${keyword.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&')}) - Group 1: a keyword value with escaped special chars
• (?!\\w) - a negative lookahead that fails the match if there is a word char immediately to the right of the current location.

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