Question

For a form validation I’ve to check input with javascript for valid names
The string has to fit the following pattern.

• I may not start or end with a space
• It may contain spaces
• It may contain capital en lowercase letters, inclusive ê è en such
• It may symbols like – ‘ “
• It must contain at least 1 character

This RegExp does the job almost:

[a-zA-ZàáâäãåèéêëìíîïòóôöõøùúûüÿýñçčšžÀÁÂÄÃÅÈÉÊËÌÍÎÏÒÓÔÖÕØÙÚÛÜŸÝÑßÇŒÆČŠŽ∂ð ,.'-]

But this RegExp doesn’t check for spaces at start of end.

Which JS RegExp requires the requirements mentioned above?

Thanks in advance

Answer 1

Here is my take on the topic:

if (subject.match(/^(?=\S+)(?=[a-zA-ZàáâäãåèéêëìíîïòóôöõøùúûüÿýñçčšžÀÁÂÄÃÅÈÉÊËÌÍÎÏÒÓÔÖÕØÙÚÛÜŸÝÑßÇŒÆČŠŽ∂ð ,.'-]*$).*(?=\S).$/)) {
    // Successful match
}

It basically says, start with at least something which isn’t a space. So here goes conditions 1 and 5.

Then make sure that the whole thing consists of only allowed characters. Here goes all your other conditions.

Then make sure that there is at least a non space character, match it and then match tne end.

More details:

"
^                                                                                      # Assert position at the beginning of the string
(?=                                                                                    # Assert that the regex below can be matched, starting at this position (positive lookahead)
   \S                                                                                     # Match a single character that is a “non-whitespace character”
      +                                                                                      # Between one and unlimited times, as many times as possible, giving back as needed (greedy)
)
(?=                                                                                    # Assert that the regex below can be matched, starting at this position (positive lookahead)
   [a-zA-ZàáâäãåèéêëìíîïòóôöõøùúûüÿýñçčšžÀÁÂÄÃÅÈÉÊËÌÍÎÏÒÓÔÖÕØÙÚÛÜŸÝÑßÇŒÆČŠŽ∂ð ,.'-]       # Match a single character present in the list below
                                                                                             # A character in the range between “a” and “z”
                                                                                             # A character in the range between “A” and “Z”
                                                                                             # One of the characters “àáâäãåèéêëìíîïòóôöõøùúûüÿýñçcšžÀÁÂÄÃÅÈÉÊËÌÍÎÏÒÓÔÖÕØÙÚÛÜŸÝÑßÇŒÆCŠŽ?ð ,.”
                                                                                             # The character “'”
                                                                                             # The character “-”
      *                                                                                      # Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
   $                                                                                      # Assert position at the end of the string (or before the line break at the end of the string, if any)
)
.                                                                                      # Match any single character that is not a line break character
   *                                                                                      # Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
(?=                                                                                    # Assert that the regex below can be matched, starting at this position (positive lookahead)
   \S                                                                                     # Match a single character that is a “non-whitespace character”
)
.                                                                                      # Match any single character that is not a line break character
$                                                                                      # Assert position at the end of the string (or before the line break at the end of the string, if any)
"