javascript - 在 JavaScript 中匹配一个单词而不匹配另一个单词的正则表达式

Question

我想匹配包含字符串 yes 的表达式，但前提是它前面没有字符串 no。

例如，这与匹配:Hello world, major yes here!
但这不会匹配:Hell no yes

第二个字符串不匹配，因为 yes 字符串前面是 no 字符串。显然这需要否定的后视，它不是以 JavaScript 正则表达式的形式实现的，我试过这样的东西:/((?!no ))yes/
/^(?!.*no) 是$/

但他们似乎并没有达到预期的效果:/

Answer 1

你可以试试下面的正则表达式。

^(?=(?:(?!\bno\b).)*yes).*

DEMO

解释:

^                        the beginning of the string
(?=                      look ahead to see if there is:
  (?:                      group, but do not capture (0 or more
                           times):
    (?!                      look ahead to see if there is not:
      \b                       the boundary between a word char
                               (\w) and something that is not a
                               word char
      no                       'no'
      \b                       the boundary between a word char
                               (\w) and something that is not a
                               word char
    )                        end of look-ahead
    .                        any character except \n
  )*                       end of grouping
  yes                      'yes'
)                        end of look-ahead
.*                       any character except \n (0 or more times)