I've got this RegEx which is used to validate what the user enters
It must be a value 8 - 16 characters long and can contain ONE of the certain special characters.
/^(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[:;#~]).{8,16}$"
I'm not trying to show an alert if the user enters something that doesn't match the above. So a-z, A-Z, 0-9 and :;#~ are allowed but anything else shows an alert.
So Abcd1234# is OK, but if they enter Abcd1234!$ if will show the alert as ! & $ are not in the match.
I've tried adding ^ to the start of character match to try and negate them, but that didn't work.
What's the best way to do this?
It seems you only need to allow the characters mentioned in the lookaheads, create a character class with them and replace the last . with it:
/^(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[:;#~])[\da-zA-Z:;#~]{8,16}$/
^^^^^^^^^^^^^^
See the regex demo
The [\da-zA-Z:;#~]{8,16} pattern will match 8 to 16 chars that are either digits, ASCII letters, or :, ;, # or ~ symbols.
Details:
^ - start of string
(?=.*\d) - there must be a digit after any 0+ chars other than line break chars (a (?=\D*\d) will be more efficient as it is based on the contrast principle)
(?=.*[a-z]) - - there must be an ASCII lowercase letter after any 0+ chars other than line break chars (a (?=[^a-z]*[a-z]) will be more efficient)
(?=.*[A-Z]) - there must be an ASCII uppercase letter after any 0+ chars other than line break chars (a (?=[^A-Z]*[A-Z]) will be more efficient)
(?=.*[:;#~]) - there must be a :, ;, # or ~ after any 0+ chars other than line break chars (you may also use (?=[^:;#~]*[:;#~]))
[\da-zA-Z:;#~]{8,16} - 8 to 16 chars defined in the character class
$ - end of string.
Related
Allowable characters:
uppercase A to Z
lowercase a to z
hyphen
apostrophe
single quote
space
full stop
numerals 0 to 9
validations:
Must contain alphabetic characters
Cannot have consecutive non alpha characters except for full stop followed by a space OR apostrophe can be followed by a space
Cannot have non-alphabetic characters at the start (except for apostrophe)
Can end with a full stop
I have a regex with the below validation. Use this as reference
/^(?=[a-zA-Z0-9`'. -]+$)(?!.*[0-9'` -]{2})[a-zA-Z'][^\r\n.]*(?:\.[ a-z][^\r\n.]*)*$/;
Need to add the below validations to the above regex
Can end with a full stop
An apostrophe can be followed by a space.
Examples Valid
'Andy
Andy.
Andy' De'Wall
Andy. DeWa2e
A2dy'
Examples Invalid
2Andy
A2'ndy.
Andy'-Wall
Andy. DeWa23
A24dy'
You could:
assert not 2 consecutive digits . ' or -
assert not a digit or hyphen or space followed by a space
assert at least a char A-Z a-z
start the match with either ' or a char A-Z a-z
For example
^(?!.*[0-9.'-]{2})(?!.*[0-9 -] )(?=[^A-Za-z\n]*[A-Za-z])[A-Za-z'][A-Za-z0-9.' -]*$
Regex demo
I'm trying to create a regular expression that matches strings such as:
N1-112S
So far I have succeeded with the following (although I'm not really sure why it works):
item.match(/^\D.-/)
I'd like to further bolster the results by ensuring that the last character is A-Z as well.
I'd appreciate some help on a good regular expression for matching this pattern. Thanks!
If you plan to match a string that starts with an uppercase ASCII letter, then has a digit, then a hyphen, then 1 or more digits and then an ASCII letter at the end of the string use
/^[A-Z]\d-\d+[A-Z]$/.test(item)
See the regex demo. Also, to test if a regex matches some string or not, I'd recommend RegExp#test.
Pattern details
^ - start of string
[A-Z] - an uppercase ASCII letter
\d - an ASCII digit
- - a hyphen
\d+ - 1+ digits
[A-Z] - an ASCII letter
$ - end of string.
Variations
To match any alphanumeric chars after hyphen till the end of string, you need to change the above pattern a bit:
/^[A-Z]\d-[\dA-Z]*[A-Z]$/
The second \d+ is changed to [\dA-Z]*, any 0 or more ASCII digits or letters.
If there can be any chars after -, use .* or [^] instead of a \d+:
/^[A-Z]\d-.*[A-Z]$/
I need a regex to validate,
Should be of length 18
First 5 characters should be either (xyz34|xyz12)
Remaining 13 characters should be alphanumeric only letters and numbers, no whitespace or special characters is allowed.
I have a pattern like here, '/^(xyz34|xyz12)((?=.*[a-zA-Z])(?=.*[0-9])){13}/g'
But this is allowing whitespace and special characters like ($,% and etc) which is violating the rule #3.
Any suggestion to exclude this whitespace and special characters and to strictly check that it must be letters and numbers?
You should not quantify lookarounds. They are non-consuming patterns, i.e. the consecutive positive lookaheads check the presence of their patterns but do not advance the regex index, they check the text at the same position. It makes no sense repeating them 13 times. ^(xyz34|xyz12)((?=.*[a-zA-Z])(?=.*[0-9])){13} is equal to ^(xyz34|xyz12)(?=.*[a-zA-Z])(?=.*[0-9]), and means the string can start with xyz34 or xyz12 and then should have at least 1 letter and at least 1 digits.
You may consider fixing the issue by using a consuming pattern like this:
If you do not care if the last 13 chars contain only digits or only letters, use the patterns suggested by other users, like /^(?:xyz34|xyz12)[a-zA-Z\d]{13}$/ or /^xyz(?:34|12)[a-zA-Z0-9]{13}$/
If there must be at least 1 digit and at least 1 letter among those 13 alphanumeric chars, use /^xyz(?:34|12)(?=[a-zA-Z]*\d)(?=\d*[a-zA-Z])[a-zA-Z\d]{13}$/.
See the regex demo #1 and the regex demo #2.
NOTE: these are regex literals, do not use them inside single- or double quotes!
Details
^ - start of string
xyz - a common prefix
(?:34|12) - a non-capturing group matching 34 or 12
(?=[a-zA-Z]*\d) - there must be at least 1 digit after any 0+ letters to the right of the current location
(?=\d*[a-zA-Z]) - there must be at least 1 letter after any 0+ digtis to the right of the current location
[a-zA-Z\d]{13} - 13 letters or digits
$ - end of string.
JS demo:
var strs = ['xyz34abcdefghijkl1','xyz341bcdefghijklm','xyz34abcdefghijklm','xyz341234567890123','xyz14a234567890123'];
var rx = /^xyz(?:34|12)(?=[a-zA-Z]*\d)(?=\d*[a-zA-Z])[a-zA-Z\d]{13}$/;
for (var s of strs) {
console.log(s, "=>", rx.test(s));
}
.* will match any string, for your requirment you can use this:
/^xyz(34|12)[a-zA-Z0-9]{13}$/g
regex fiddle
/^(xyz34|xyz12)[a-zA-Z0-9]{13}$/
This should work,
^ asserts position at the start of a line
1st Capturing Group (xyz34|xyz12)
1st Alternative xyz34 matches the characters xyz34 literally (case sensitive)
2nd Alternative xyz12 matches the characters xyz12 literally (case sensitive)
Match a single character present in the list below [a-zA-Z0-9]{13}
{13} Quantifier — Matches exactly 13 times
I have the following javascript regex:
/^[^\s][a-z0-9 ]+[^\s]$/i
I need to allow any alphanumeric character as well as spaces inside the string but not at the beginning nor at the end.
Oddly enough, the above regex will not accept less than 3 characters, e.g. aa will not match but aaa will.
I am not sure why. Can anyone please help ?
You have: [^\s] (requires matching at least one non-whitespace character), [a-z0-9 ]+ (requires matching at least one alphanumeric or space character), and [^\s] again (requires matching at least one non-whitespace character). So, in total, you need at least 3 characters in the string.
Use word boundaries at the beginning and end instead:
/^\b[a-z0-9 ]+\b$/i
https://regex101.com/r/2GhH3N/1
Try the following regex:
^(?! )[a-z0-9 ]*[a-z0-9]$
Details:
^(?! ) - Start of the string and no space after it (so here we exclude the
initial space).
[a-z0-9 ]* - A sequence of letters, digits and spaces, possibly empty
(the content before the last letter(see below).
[a-z0-9]$ - The last letter and the end of string (so here we exclude the
terminal space).
You should re-write the expression as
/^[a-z0-9]+(?:\s+[a-z0-9]+)*$/i
See the regex demo.
NOTE: If only one whitespace is allowed between the alphanumeric chars use
/^[a-z0-9]+(?:\s[a-z0-9]+)*$/i
^^
Details
^ - start of string
[a-z0-9]+ - 1+ letters/digits
(?:\s+[a-z0-9]+)* - 0 or more repetitions of 1+ whitespaces (\s+) and 1+ digit/letters
$ - end of string.
See the regex graph:
I have a requirement, where i have to validate a field in Excel.
Validations:
Field should start and end with [a-zA-Z0-9] but not with any special chars [-_]
It cannot contain "-" and "_" continuously more than once.
Example:
A--Badasd (Not allowed)
A__Bsdasdas (Not allowed)
A-_fdsfdsd (Not Allowed)
A_-sfsdfsdf (Not allowed)
A-B-adf (allowed)
A_b_adads (allowed)
I came up with this following regex, however, it doesn't seem to accept even the non-continuous entries of "-" and "_".
^[a-zA-z0-9]+(([\xFF01-\xFF5E]+|[\\-\\_])+)[a-zA-Z0-9]+$
[\xFF01-\xFF5E] is to not allow any double width characters, so please ignore it as it is working fine.
Any help would be greatly appreciable.
I can only suggest a lookahead based pattern (as [\xFF01-\xFF5E] matches _ and restricting it in JS regex will make the pattern more cumbersome):
/^[a-z0-9](?:(?!.*?[-_]{2})[\xFF01-\xFF5E-]*[a-z0-9])?$/i
See the regex demo.
This pattern will match strings of 1 char length, too, and will only match those strings starting and ending with an ASCII alphanumeric char and not having --, _-, -_ and __ in them.
If you want to "block" strings of length 1, i.e. set the minimum match length to 2, you should remove (?: and )? from the pattern above:
/^[a-z0-9](?!.*?[-_]{2})[\xFF01-\xFF5E-]*[a-z0-9]$/i
Details
^ - start of string
[a-z0-9] - an alphanumeric ASCII char
(?:(?!.*?[-_]{2})[\xFF01-\xFF5E_-]*[a-z0-9])? - an optional (1 or 0 occurrences) sequence of:
(?!.*?[-_]{2}) - a lookahead check that will fail the match if there are 2 consecutive - or _ anywhere after any 0+ chars other than line break chars
[\xFF01-\xFF5E-]* - any char in the \xFF01-\xFF5E range or/and -
[a-z0-9] - an alphanumeric ASCII char
$ - end of string.