Works in Chrome, but breaks in Safari: Invalid regular expression: invalid group specifier name
/^(?=.{1,50}$)(?![_.-])(?!.*[_.-]{2})[a-z0-9._-] (?<![_.-])$/
CodePudding user response：
Guess the lookbehind is not supported by Safari JS regex. Good news, it's not needed here.
^(?![_.-])(?!.*[_.-]{2})[a-z\d._-]{0,49}[a-z\d]$
Just another (self explaining) way to write the pattern without the lookbehind at the end.
CodePudding user response：
You can also use a singe lookahead assertion for the length, and then start and end the match with a char a-z0-9 not allowing consecutive matches for [._-]
^(?=.{1,50}$)[a-z\d] (?:[._-][a-z\d] )*$
Explanation
^Start of string(?=.{1,50}$)Positive lookahead, assert 50 chars till the end of string[a-z\d]Match 1 chars a-z0-9(?:Non capture group[._-][a-z\d]Match one of._
)*Close the non capture group and optionally repeat it$End of string