Javascript 我想限制正则表达式中子域的数目_Javascript_Regex

Javascript 我想限制正则表达式中子域的数目

javascript regex

Javascript 我想限制正则表达式中子域的数目,javascript,regex,Javascript,Regex,我想限制子域的级别仅为3级。尝试下面的正则表达式失败 ([\.]?[a-z]*){3} 我的目标：abc.def.ghi 但是上面的正则表达式接受abc.def.ghi。（注意最后一个）使用 ^（？[a-z]+（？：\[a-z]+）{0,2}）$ 看解释 -------------------------------------------------------------------------------- ^ the beginn

我想限制子域的级别仅为3级。尝试下面的正则表达式失败

([\.]?[a-z]*){3}

我的目标：

abc.def.ghi

但是

上面的正则表达式接受abc.def.ghi。（注意最后一个

）

使用

^（？[a-z]+（？：\[a-z]+）{0,2}）$

看

解释

--------------------------------------------------------------------------------
  ^                        the beginning of the string
--------------------------------------------------------------------------------
  (?:                      group, but do not capture (optional
                           (matching the most amount possible)):
--------------------------------------------------------------------------------
    [a-z]+                   any character of: 'a' to 'z' (1 or more
                             times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    (?:                      group, but do not capture (between 0 and
                             2 times (matching the most amount
                             possible)):
--------------------------------------------------------------------------------
      \.                       '.'
--------------------------------------------------------------------------------
      [a-z]+                   any character of: 'a' to 'z' (1 or
                               more times (matching the most amount
                               possible))
--------------------------------------------------------------------------------
    ){0,2}                   end of grouping
--------------------------------------------------------------------------------
  )?                       end of grouping
--------------------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string

因为regexp没有锚定，所以它匹配字符串中的任何位置。非常感谢！9分钟后接受正确答案。