Space in string allowed, but not at first or last position

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

I'll never understand why people always want to cram every validation rule into a single regex. — J. Holmes, Nov 30 '11 at 11:58
By the way even if all your conditions are met, how can you be sure that that's a name? It can be literally anything? — FailedDev, Nov 30 '11 at 12:58

score 1 · Accepted Answer · answered Nov 30 '11 at 12:19

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)
"

score 0 · Answer 2 · answered Nov 30 '11 at 11:41

0

You need to use the RegExp ^ and $ codes, which specify the start and ending respectively.

See more documentation about this.

Hope this helps!

answered Nov 30 '11 at 11:41

Leon

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stema · Answer 3 · 2011-11-30T11:50:36.927

Try this

^(?! )[a-zA-ZàáâäãåèéêëìíîïòóôöõøùúûüÿýñçčšžÀÁÂÄÃÅÈÉÊËÌÍÎÏÒÓÔÖÕØÙÚÛÜŸÝÑßÇŒÆČŠŽ∂ð ,.'-]*[a-zA-ZàáâäãåèéêëìíîïòóôöõøùúûüÿýñçčšžÀÁÂÄÃÅÈÉÊËÌÍÎÏÒÓÔÖÕØÙÚÛÜŸÝÑßÇŒÆČŠŽ∂ð,.'-]$

See it here on Regexr

^ anchors the pattern to the start of the string

$anchors the pattern to the end of the string

(?! ) is a negative lookahead that ensures, that its not starting with a space

Then there follows your character class with a * quantifier, means 0 or more times. At last there is your class once more, but without space, this is to ensure that it does not end with space.

Its a pity that Javascript regexes doesn't have Unicode support, and does not allow \p{L} for all kind of letters.

Space in string allowed, but not at first or last position

3 Answers3