Qualification check for regex - allow spaces in the middle, but not start and end
I am allowing space for this regex as follows:
JavaScript:
var re_username = /^[a-zA-Z\040\.\-]+$/;
var is_username = re_username.test($('#chatusername').val());
console.log(is_username);
... but I want to ban it at the beginning and at the end. This worked:
JavaScript:
var re_username = /^[a-zA-Z]+[a-zA-Z\040\.\-]+[a-zA-Z\.]+$/;
... but I need to enter at least 3 (<3 digits returns false, although I enter, for example A) digits for the regex to return true, which causes problems with adding classes and others ...
I found this for this, allowing spaces at the beginning and end
JavaScript:
var re_username = /^\S+(?: \S+)*$/
But this allows all characters .... How can I match my target regex? I tried this ... but it didn't work anymore.
var re_username = /^\S+([a-zA-Z]\040\S+)*$/;
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Using
var re_username = /^[a-zA-Z.-]+(?:\040+[a-zA-Z.-]+)*$/;
It will match
-
^
- beginning of line -
[a-zA-Z.-]+
- 1 + letters,.
and-
-
(?:\040+[a-zA-Z.-]+)*
- 0+ sequences-
\040+
- 1 + regular spaces -
[a-zA-Z.-]+
- 1 + letters,.
and-
-
-
$
- end of line
See regex demo .
NOTE. If you don't want to allow sequential multiple spaces, remove +
after \040
.
Another less efficient way is through lookaheads:
var re_username = /^(?!\040|.*\040$)[a-zA-Z\040.-]+$/;
^^^^^^^^^^^^^^^
Here, a negative lookahead (?!\040|.*\040$)
will fail if a space is found at the beginning of the line or after any 0+ ( .*
) characters at the end of the line ( $
).
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