Javascript regex for specific name validation

Question

I have a university assignment to write a JS regex for name validation: name can include spaces at the beginning and the end (don't ask anything, it's our teacher demand), also it can include such chars like: -, ' and space (" "). At the moment, my regex looks like that:

var Nameregex = /^( ?)*[A-Z]+((['-])?[a-z]+)*(([ ]?[a-z]*)*)*$/g;

It works almost perfect, but except for one case: one word (words separated from each other with spaces and - symbols) can contain only one ' symbol.

For example, names like John-andrew'andrew'john shouldn't work. But John-andrew'john-andrew'john should work.

Ryszard Czech · Accepted Answer · 2020-10-30 22:12:33Z

Add a (?!.*'[A-Za-z]+') negative lookahead after ^:

/^(?!.*'[A-Za-z]+')\s*[A-Z]+(?:['-]?[a-z]+)*(?:\s*[a-z]*)*$/

See proof

Explanation

--------------------------------------------------------------------------------
  ^                        the beginning of the string
--------------------------------------------------------------------------------
  (?!                      look ahead to see if there is not:
--------------------------------------------------------------------------------
    .*                       any character except \n (0 or more times
                             (matching the most amount possible))
--------------------------------------------------------------------------------
    '                        '\''
--------------------------------------------------------------------------------
    [A-Za-z]+                any character of: 'A' to 'Z', 'a' to 'z'
                             (1 or more times (matching the most
                             amount possible))
--------------------------------------------------------------------------------
    '                        '\''
--------------------------------------------------------------------------------
  )                        end of look-ahead
--------------------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (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 (0 or more times
                           (matching the most amount possible)):
--------------------------------------------------------------------------------
    ['-]?                    any character of: ''', '-' (optional
                             (matching the most amount possible))
--------------------------------------------------------------------------------
    [a-z]+                   any character of: 'a' to 'z' (1 or more
                             times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
  )*                       end of grouping
--------------------------------------------------------------------------------
  (?:                      group, but do not capture (0 or more times
                           (matching the most amount possible)):
--------------------------------------------------------------------------------
    \s*                      whitespace (\n, \r, \t, \f, and " ") (0
                             or more times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    [a-z]*                   any character of: 'a' to 'z' (0 or more
                             times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
  )*                       end of grouping
--------------------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string

Thanks! It works almost perfectly. Forgot to mention, that names like John andrew'john andrew'john also should work. So, the final regex looks like: /^(?!.*'[A-Za-z]+') *[A-Z]+(?:[ '-]?[a-z]+)*(?:\s[a-z]*)*$/ There is added space character in the third character set. Thanks again for the help :)

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