This question already has answers here:
RegEx for Phone number in JavaScript
(3 answers)
Closed 8 years ago.
I am a beginner in regex.
I need a regular expression which satisfies following criteria. I tried lot of things but couldn't make it.
total no. of digits can be 10, 11 or 12
expression can except characters like -, (, ), space, /, \
expression can start with any digit/character mentioned above
max length of the expression is 16.
All digits and characters can appear in random order in expression
Can anyone please help me?
this pattern seems to work as requested ^(?=(?:\D*\d){10,12}\D*$)[0-9 \-()\\\/]{1,16}$
Demo
The expression [ 0-9()\-/\\]{10,16} fulfills all your requirements.
[...] is a positive character class definition. A matching character can be one of the characters in the square brackets.
The first character in the square brackets is a space character.
0-9 defines all digits (from charcter 0 to character 9). \d could be also used for any digit.
( and ) are also valid characters.
The character - has a special meaning in square brackets as you can see on 0-9 and therefore must be escaped in square brackets by the backslash character when it should be interpreted as literal character.
The slash is the next character. Please note that also the slash must be escaped with a backslash when using this regular expression in a JavaScript RegExp object.
And the last character with the square brackets is the backslash character which must be always escaped with one more backslash as it is the escape character if the backslash should be interpreted as literal character.
{10,16} ... means that the preceding expression must be positively applied on a string for at least 10 but not more than 16 characters.
But you should really search for expressions matching phone numbers in WWW as this is a very often needed expression. You should not reinvent the wheel respectively the expression.
I recommend using http://regexlib.com for your RegEx needs. Very good site with tons of RegEx's that you can browse on. I also recommend http://regex101.com for testing regular expressions. Has a very great tool to help you build/modify/test your expressions.
Related
This question already has answers here:
Why does character range class [A-z] match underscore?
(1 answer)
Reference - What does this regex mean?
(1 answer)
Closed 4 years ago.
Regular expressions that have [] have always confused me a bit. Below are some common patterns for the use of []
/[0-9]/ Captures all numbers
/[A-Z]/ Captures all 26 uppercase letters
/[a-z]/ captures all 26 lowercase letters
But what about
/[A-Za-z0-9] captures all numbers, uppercase letters, and lowercase letters
Which could also be written as
/[0-z] which also captures all numbers, uppercase letters, and lowercase letters. But it also captures ^ and | as well, among other characters
why is this?
Its because of ASCII Tables
/[0-z] captures all ASCII values from 48 to 122
[A-Za-z0-9] does not
The [] in a regular expression denotes a character set. It tells the pattern matcher to match any character that appears inside the brackets. So, for instance,
/[abc]/
will match any one of 'a', 'b', or 'c'.
Inside the brackets, however, the hyphen ('-') has a special meaning: it denotes the entire range of characters between the character just before and just after the hyphen (inclusive). That is, the above regex could have been written:
/[a-c]/
If you want to include a literal hyphen in the list of characters in the set, you need to escape it. That is:
/[a\-c]/
will match any one of 'a', '-', or 'c' (and not 'b'). You can also suppress the special meaning of the hyphen by making it the first or last character in the set, so:
/[-ac]/
will also match any one of 'a', '-', or 'c'.
This explains why /[A-Za-z0-9]/ is not the same thing as /[0-z]/: the range of characters between '0' and 'z' simply includes additional characters, as you noted in your question. That's all there is to it.
As a technical detail, Javascript uses the Unicode standard to define what characters fall within a range. If you're sticking with the 7-bit ASCII character set, you'll get the same results using an ASCII chart. But don't use an ASCII chart for character codes above 0x7F. You need to consult the Unicode charts instead.
This question already has answers here:
Password REGEX with min 6 chars, at least one letter and one number and may contain special characters
(10 answers)
Closed 2 years ago.
I'm trying to create a regex validation for a password which is meant to be:
6+ characters long
Has at least one a-z
Has at least one A-Z
Has at leat one 0-9
So, in other words, the match will have :
at least one a-z, A-Z, 0-9
at least 3 any other characters
I've came up with:
((.*){3,}[a-z]{1,}[A-Z]{1,}[0-9]{1,})
it seems pretty simple and logical to me, but 2 things go wrong:
quantifier {3,} for (.*) somehow doesn't work and destroys whole regex. At first I had {6,} at the end but then regex would affect the quantifiers in inner groups, so it will require [A-Z]{6,} instead of [A-Z]{1,}
when I remove {3,} the regex works, but will match only if the groups are in order - so that it will match aaBB11, but not BBaa11
This is a use case where I wouldn't use a single regular expression, but multiple simpler ones.
Still, to answer your question: If you only want to validate that the password matches those criteria, you could use lookaheads:
^(?=.{6})(?=.*?[a-z])(?=.*?[A-Z])(?=.*?[0-9])
You're basically looking for a position from which you look at
6 characters (and maybe more to follow, doesn't matter): (?=.{6})
maybe something, then a lowercase letter: (?=.*?[a-z])
maybe something, then an uppercase letter: (?=.*?[A-Z])
maybe something, then a digit: (?=.*?[0-9])
The order of appearance is arbitrary due to the maybe something parts.
(Note that I've interpreted 6 characters long as at least 6 characters long.)
I believe this is what you want:
^(?=.*[a-z])(?=.*[A-Z])(?=.*[0-9])[!-~]{6,}$
If we follow your spec to the letter, your validation password looks like this:
^(?=.*[a-z])(?=.*[A-Z])(?=.*[0-9]).{6,}$
However, we need to improve on this, because apart from the number, lower-case and upper-case letter, are you really willing to accept any character? For instance, can the user use a character in the Thai language? A space character? A tab? Didn't think so. :)
If you want to allow all the printable ASCII characters apart from space, instead of a dot, we can use this character range: [!-~]
How does it work?
The ^ anchor makes sure we start the match at the start of the string
The (?=.*[a-z]) lookahead ensures we have a lower-case character
The (?=.*[A-Z]) lookahead ensures we have an upper-case character
The (?=.*[0-9]) lookahead ensures we a digit
The (?=.*[a-z]) lookahead ensures we have a lower-case character
The [!-~]{6,} matches six or more ASCII printable ASCII characters that are not space.
The $ ensures we have reached the end of the string (otherwise, the password could contain more characters that are not allowed).
you could use this pattern ^(?=.*[a-z])(?=.*[A-Z])(?=.*[0-9]).{6,}
I am trying to construct a regular expression which accepts alphanumerics only ([a-zA-Z0-9]), except for a single hyphen (-) in the middle of the string, with a minimum of 9 characters and a maximum of 20 characters.
I have verified the following expression, which accepts a hyphen in the middle.
/^[a-zA-Z0-9]+\-?[a-zA-Z0-9]+$/
How can I set the minimum 9 and maximum 20 characters for the above regex? I have already used quantifiers + and ? in the above expression.
How would I apply {9,20} to the above expression? Are there any other suggestions for the expression?
/^[a-zA-Z0-9]+\-?[a-zA-Z0-9]+$/
can be simplified to
/^[a-z0-9]+(?:-[a-z0-9]+)?$/i
since if there is no dash then you don't need to look for more letters after it, and you can use the i flag to match case-insensitively and avoid having to reiterate both lower-case and upper-case letters.
Then split your problem into two cases:
9-20 alpha numerics
10-21 characters, all of which are alpha numerics except one dash
You can check the second using a positive lookahead like
/^(?=.{10,21}$)/i
to check the number of characters without consuming them.
Combining these together gives you
/^(?:[a-z0-9]{9,20}|(?=.{10,21}$)[a-z0-9]+-[a-z0-9]+)$/i
You can do this provided you don't want - to be present exactly in middle
/^(?=[^-]+-?[^-]+$)[a-zA-Z\d-]{9,20}$/
[^-] matches any character that is not -
Having the following regex: ([a-zA-Z0-9//._-]{3,12}[^//._-]) used like pattern="([a-zA-Z0-9/._-]{3,12}[^/._-])" to validate an HTML text input for username, I wonder if is there anyway of telling it to check that the string has only one of the following: ., -, _
By that I mean, that I'm in need of regex that would accomplish the following (if possible)
alex-how => Valid
alex-how. => Not valid, because finishing in .
alex.how => Valid
alex.how-ha => Not valid, contains already a .
alex-how_da => Not valid, contains already a -
The problem with my current regex, is that for some reason, accepts any character at the end of the string that is not ._-, and can't figure it out why.
The other problem, is that it doesn't check to see that it contains only of the allowed special characters.
Any ideas?
Try this one out:
^(?!(.*[.|_|-].*){2})(?!.*[.|_|-]$)[a-zA-Z0-9//._-]{3,12}$
Regexpal link. The regex above allow at max one of ., _ or -.
What you want is one or more strings containing all upper, lower and digit characters
followed by either one or none of the characters in "-", ".", or "_", followed by at least one character:
^[a-zA-Z0-9]+[-|_|\.]{0,1}[a-zA-Z0-9]+$
Hope this will work for you:-
It says starts with characters followed by (-,.,_) and followed and end with characters
^[\w\d]*[-_\.\w\d]*[\w\d]$
Seems to me you want:
^[A-Za-z0-9]+(?:[\._-][A-Za-z0-9]+)?$
Breaking it down:
^: beginning of line
[A-Za-z0-9]+: one or more alphanumeric characters
(?:[\._-][A-Za-z0-9]+)?: (optional, non-captured) one of your allowed special characters followed by one or more alphanumeric characters
$: end of line
It's unclear from your question if you wanted one of your special characters (., -, and _) to be optional or required (e.g., zero-or-one versus exactly-one). If you actually wanted to require one such special character, you would just get rid of the ? at the very end.
Here's a demonstration of this regular expression on your example inputs:
http://rubular.com/r/SQ4aKTIEF6
As for the length requirement (between 3 and 12 characters): This might be a cop-out, but personally I would argue that it would make more sense to validate this by just checking the length property directly in JavaScript, rather than over-complicating the regular expression.
^(?=[a-zA-Z0-9/._-]{3,12}$)[a-zA-Z0-9]+(?:[/._-][a-zA-Z0-9]+)?$
or, as a JavaScript regex literal:
/^(?=[a-zA-Z0-9\/._-]{3,12})[a-zA-Z0-9]+(?:[\/._-][a-zA-Z0-9]+)?$/
The lookahead, (?=[a-zA-Z0-9/._-]{3,12}$), does the overall-length validation.
Then [a-zA-Z0-9]+ ensures that the name starts with at least one non-separator character.
If there is a separator, (?:[/._-][a-zA-Z0-9]+)? ensures that there's at least one non-separator following it.
Note that / has no special meaning in a regex. You only have to escape it if you're using a regex literal (because / is the regex delimiter), and you escape it by prefixing with a backslash, not another forward-slash. And inside a character class, you don't need to escape the dot (.) to make it match a literal dot.
The dot in regex has a special meaning: "any character here".
If you mean a literal dot, you should escape it to tell the regex parser so.
Escape dot in a regex range
I have a regular expression ^(?=.*?[A-Za-z])\S*$ which indicates that the input should contain alphabets and can contain special characters or digits along with the alphabets. But it is not allowing white spaces since i have used \S.
Can some one suggest me a reg exp which should contain alphabets and it can contain digits or special characters and white space but alphabets are must and the last character should not end with a white space
Quite simply:
^(?=.*?[A-Za-z]).*$
Note that in JavaScript . doesn't match new lines, and there is no dot-all flag (/s). You can use something like [\s\S] instead if that is an issue:
^(?=[\s\S]*?[A-Za-z])[\s\S]*$
Since you only have a single lookahead, you can simplify the pattern to:
^.*[A-Za-z].*$
Or, even simpler:
[A-Za-z]
[A-Za-z] will match if it finds a letter anywhere in the string, you don't really need to search the rest from start to end.
To also validate the last character isn't a whitespace, it is probably easiest to use the lookahead again (as it basically means AND in regular expressions:
^(?=.*?[A-Za-z]).*\S$