Invalid regular expression, Invalid group Javascript Regex-CodePudding

I have a C# code that check's for falseNumber on regex basis:

public bool falseNumber(string num)
    {
        try
        {
            num = num.Replace("-", "");
            string re = @"(?x)
            ^
            # fail if...
            (?!
                # repeating numbers
                (\d) \1  $
                |
                # sequential ascending
                (?:0(?=1)|1(?=2)|2(?=3)|3(?=4)|4(?=5)|5(?=6)|6(?=7)|7(?=8)|8(?=9)|9(?=0)){5} \d $
                |
                # sequential descending
                (?:0(?=9)|1(?=0)|2(?=1)|3(?=2)|4(?=3)|5(?=4)|6(?=5)|7(?=6)|8(?=7)|9(?=8)){5} \d $
            )
            # match any other combinations of 6 digits
            \d 
            $
        ";
            return Regex.IsMatch(num, re);
        }
        catch (Exception y) { return true; }
    }

I need this code to be converted to JS, so I have written:

const falseNumber = (num) =>
{
  num = num.replaceAll("-", "");
  let re = /(?x)^(?!(\d)\1 $|(?:0(?=1)|1(?=2)|2(?=3)|3(?=4)|4(?=5)|5(?=6)|6(?=7)|7(?=8)|8(?=9)|9(?=0)){5}\d$|(?:0(?=9)|1(?=0)|2(?=1)|3(?=2)|4(?=3)|5(?=4)|6(?=5)|7(?=6)|8(?=7)|9(?=8)){5}\d$)\d $/
  return re.test(num);
}

But that gives me error:

VM46:5 Uncaught SyntaxError: Invalid regular expression: /((?x)^(?!(\d) \1 $|(?:0(?=1)|1(?=2)|2(?=3)|3(?=4)|4(?=5)|5(?=6)|6(?=7)|7(?=8)|8(?=9)|9(?=0)){5} \d $|(?:0(?=9)|1(?=0)|2(?=1)|3(?=2)|4(?=3)|5(?=4)|6(?=5)|7(?=6)|8(?=7)|9(?=8)){5} \d $)\d $)/: Invalid group at falseNumber (:5:12) at :1:1

Any help would be highly appreciated.

Thank you.

const falseNumber = (num) =>
{
  num = num.replaceAll("-", "");
  let re = /(?x)^(?!(\d)\1 $|(?:0(?=1)|1(?=2)|2(?=3)|3(?=4)|4(?=5)|5(?=6)|6(?=7)|7(?=8)|8(?=9)|9(?=0)){5}\d$|(?:0(?=9)|1(?=0)|2(?=1)|3(?=2)|4(?=3)|5(?=4)|6(?=5)|7(?=6)|8(?=7)|9(?=8)){5}\d$)\d $/
  return re.test(num);
}


console.log(falseNumber('33-3333333-33'));

CodePudding user response：

x modifier is not built in JS that's why you get an error. And in your case, you don't need to use x modifier because you don't use comments or have any whitespace in your regex expression in JS.

x modifier definition:

This flag tells the engine to ignore all whitespace and allow for comments in the regex; also called verbose. Comments are indicated by a starting "#"-character. If you need to include a space character in your regex, it must now be escaped '\ '.

const falseNumber = (num) =>
{
  num = num.replaceAll("-", "");
  let re = /^(?!(\d)\1 $|(?:0(?=1)|1(?=2)|2(?=3)|3(?=4)|4(?=5)|5(?=6)|6(?=7)|7(?=8)|8(?=9)|9(?=0)){5}\d$|(?:0(?=9)|1(?=0)|2(?=1)|3(?=2)|4(?=3)|5(?=4)|6(?=5)|7(?=6)|8(?=7)|9(?=8)){5}\d$)\d $/
  return re.test(num);
}


console.log(falseNumber('33-3333333-33'));