字边界断言：\\b，\\B

¥Syntax

\b
\B

¥Description

\b 断言字符串中的当前位置是字边界。\B 否定该断言：它断言当前位置不是字边界。两者都是断言，因此与其他 字符转义 或 字符类转义 不同，\b 和 \B 不消耗任何字符。

¥\b asserts that the current position in the string is a word boundary. \B negates the assertion: it asserts that the current position is not a word boundary. Both are assertions, so unlike other character escapes or character class escapes, \b and \B don't consume any characters.

一个单词字符包括以下内容：

¥A word character includes the following:

• 字母（A–Z、a–z）、数字（0–9）和下划线（_）。
• 如果正则表达式为 Unicode 感知 并且设置了 i 标志，则其他 Unicode 字符将通过 表壳折叠 规范化为上述字符之一。

单词字符也由 \w 字符类转义 匹配。

¥Word characters are also matched by the \w character class escape.

越界输入位置被视为非单词字符。例如，以下是成功匹配：

¥Out-of-bounds input positions are considered non-word characters. For example, the following are successful matches:

/\ba/.exec("abc");
/c\b/.exec("abc");

/\B /.exec(" abc");
/ \B/.exec("abc ");

¥Examples

¥Detecting words

以下示例检测字符串是否包含单词 "thanks" 或 "谢谢"：

¥The following example detects if a string contains the word "thanks" or "thank you":

function hasThanks(str) {
  return /\b(thanks|thank you)\b/i.test(str);
}

hasThanks("Thanks! You helped me a lot."); // true
hasThanks("Just want to say thank you for all your work."); // true
hasThanks("Thanksgiving is around the corner."); // false

警告：并非所有语言都有明确定义的单词边界。如果你使用的是中文或泰语等没有空格分隔符的语言，请使用更高级的库（如 Intl.Segmenter）来搜索单词。

¥Warning: Not all languages have clearly defined word boundaries. If you are working with languages like Chinese or Thai, where there are no whitespace separators, use a more advanced library like Intl.Segmenter to search for words instead.

¥See also

• 断言 指南
• 正则表达式
• 输入边界断言：^、$
• 前瞻断言：(?=...)、(?!...)
• 后向断言：(?<=...)、(?<!...)
• 字符转义：\n、\u{...}