Regular Expression. 20 Alphabetical letters and up to 2 of ( . - _ ) - javascript

I'm trying to build up a regex pattern for the html input field which only allows up to 20 combined alphabetical letters and digits which can only have up to two of Dashes(-), Underscores(_) and fullstops (.)
So something like only two of the symbols allowed and any amount of letters and digits allowed, combined they've got to be between 4 and 20.
What would the pattern for this be?
An sample (non functioning) version could be like [A-Za-z0-9([\._-]{0,2})]{4,20}
Solution:
I decided to go with #pascalhein #Honore Doktorr answer which is to use a lookahead.
The final pattern is ^(?=[A-Za-z0-9]*([._-][A-Za-z0-9]*){0,2}$)[A-Za-z0-9._-]{4,20}$

You can verify the length with a lookahead at the beginning:
^(?=.{4,20}$)
Then list all the cases that are allowed for your regex separately:
[A-Za-z0-9]* (no special chars)
[A-Za-z0-9]*[._-][A-Za-z0-9]* (one special char)
[A-Za-z0-9]*[._-][A-Za-z0-9]*[._-][A-Za-z0-9]* (two special chars)
It isn't beautiful, but I believe it should work. This is the final expression:
^(?=.{4,20}$)([A-Za-z0-9]*|[A-Za-z0-9]*[._-][A-Za-z0-9]*|[A-Za-z0-9]*[._-][A-Za-z0-9]*[._-][A-Za-z0-9]*)$
Edit:
Actually, it might be nicer to test the number of special characters with a lookahead instead:
^(?=[A-Za-z0-9]*([._-][A-Za-z0-9]*){0,2}$)[A-Za-z0-9._-]{4,20}$

I encourage you to not to use a Regex when there are functions for the porpuse you want to achieve.
An advice I give to jrs on this topic is to use a regex for single porpuses, if there is more than one porpuse, use more regex.
to answer your question:
1 your valid characters from start to end.
var 1stregex = /^[A-Za-z0-9._-]{4,20}$/;
2 Count must be 0 to 2, which in javascript is .match().length.
var 2ndregex = /([._-])/;
if(myText.match(1stregex) && myText.match(2ndregex).length <=2)
{ isvalid=true; }

Related

JQuery match with RegEx not working

I have a filename that will be something along the lines of this:
Annual-GDS-Valuation-30th-Dec-2016-082564K.docx
It will contain 5 numbers followed by a single letter, but it may be in a different position in the file name. The leading zero may or may not be there, but it is not required.
This is the code I come up with after checking examples, however SelectedFileClientID is always null
var SelectedFileClientID = files.match(/^d{5}\[a-zA-Z]{1}$/);
I'm not sure what is it I am doing wrong.
Edit:
The 0 has nothing to do with the code I am trying to extract. It may or may not be there, and it could even be a completely different character, or more than one, but has nothing to do with it at all. The client has decided they want to put additional characters there.
There are at least 3 issues with your regex: 1) the pattern is enclosed with anchors, and thus requires a full string match, 2) the d matches a letter d, not a digit, you need \d to match a digit, 3) a \[ matches a literal [, so the character class is ruined.
Use
/\d{5}[a-zA-Z]/
Details:
\d{5} - 5 digits
[a-zA-Z] - an ASCII letter
JS demo:
var s = 'Annual-GDS-Valuation-30th-Dec-2016-082564K.docx';
var m = s.match(/\d{5}[a-zA-Z]/);
console.log(m[0]);
All right, there are a few things wrong...
var matches = files.match(/\-0?(\d{5}[a-zA-Z])\.[a-z]{3,}$/);
var SelectedFileClientID = matches ? matches[1] : '';
So:
First, I get the matches on your string -- .match()
Then, your file name will not start with the digits - so drop the ^
You had forgotten the backslash for digits: \d
Do not backslash your square bracket - it's here used as a regular expression token
no need for the {1} for your letters: the square bracket content is enough as it will match one, and only one letter.
Hope this helps!
Try this pattern , \d{5}[a-zA-Z]
Try - 0?\d{5}[azA-Z]
As you mentioned 0 may or may not be there. so 0? will take that into account.
Alternatively it can be done like this. which can match any random character.
(\w+|\W+|\d+)?\d{5}[azA-Z]

javascript regex : possible to have a range in the quantifier? [duplicate]

I've written a regular expression that matches any number of letters with any number of single spaces between the letters. I would like that regular expression to also enforce a minimum and maximum number of characters, but I'm not sure how to do that (or if it's possible).
My regular expression is:
[A-Za-z](\s?[A-Za-z])+
I realized it was only matching two sets of letters surrounding a single space, so I modified it slightly to fix that. The original question is still the same though.
Is there a way to enforce a minimum of three characters and a maximum of 30?
Yes
Just like + means one or more you can use {3,30} to match between 3 and 30
For example [a-z]{3,30} matches between 3 and 30 lowercase alphabet letters
From the documentation of the Pattern class
X{n,m} X, at least n but not more than m times
In your case, matching 3-30 letters followed by spaces could be accomplished with:
([a-zA-Z]\s){3,30}
If you require trailing whitespace, if you don't you can use: (2-29 times letter+space, then letter)
([a-zA-Z]\s){2,29}[a-zA-Z]
If you'd like whitespaces to count as characters you need to divide that number by 2 to get
([a-zA-Z]\s){1,14}[a-zA-Z]
You can add \s? to that last one if the trailing whitespace is optional. These were all tested on RegexPlanet
If you'd like the entire string altogether to be between 3 and 30 characters you can use lookaheads adding (?=^.{3,30}$) at the beginning of the RegExp and removing the other size limitations
All that said, in all honestly I'd probably just test the String's .length property. It's more readable.
This is what you are looking for
^[a-zA-Z](\s?[a-zA-Z]){2,29}$
^ is the start of string
$ is the end of string
(\s?[a-zA-Z]){2,29} would match (\s?[a-zA-Z]) 2 to 29 times..
Actually Benjamin's answer will lead to the complete solution to the OP's question.
Using lookaheads it is possible to restrict the total number of characters AND restrict the match to a set combination of letters and (optional) single spaces.
The regex that solves the entire problem would become
(?=^.{3,30}$)^([A-Za-z][\s]?)+$
This will match AAA, A A and also fail to match AA A since there are two consecutive spaces.
I tested this at http://regexpal.com/ and it does the trick.
You should use
[a-zA-Z ]{20}
[For allowed characters]{for limiting of the number of characters}

Regex allowing only alphanumeric and special characters does not work

I have constructed the following Regex, which allows strings that only satisfy all three conditions:
Allows alphanumeric characters.
Allows special characters defined in the Regex.
String length must be min 8 and max 20 characters.
The Regex is:
"^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[$#$!%*?&])[A-Za-z\d$#$!%*?&]$"
I use the following Javascript code to verify input:
var regPassword = new RegExp("^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[$#$!%*?&])[A-Za-z\d$#$!%*?&]$");
regPassword.test(form.passwordField.value);
The test() method returns false for such inputs as abc123!ZXCBN. I have tried to locate the problem in the Regex without any success. What causes the Regex validation to fail?
I see two major problems. One is that inside a string "...", backslashes \ have a special meaning, independent of their special meaning inside a regex. In particular, \d ends up just becoming d — not what you want. The best fix for that is to use the /.../ notation instead of new RegExp("..."):
var regPassword = /^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[$#$!%*?&])[A-Za-z\d$#$!%*?&]$/;
The other problem is that your regex doesn't match your requirements.
Actually, the requirements that you've stated don't really make sense, but I'm guessing you want something like this:
Must contain at least one lowercase letter, at least one uppercase letter, at least one digit, and at least one of the special characters $#$!%*?&.
Can only contain lowercase letters, uppercase letters, digits, and the special characters $#$!%*?&.
Total length must be between 8 and 20 characters, inclusive.
If so, then you've managed #1 and #2, but forgot about #3. Right now your regex demands that the length be exactly 1. To fix this, you need to add {8,20} after the [A-Za-z\d$#$!%*?&] part:
var regPassword = /^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[$#$!%*?&])[A-Za-z\d$#$!%*?&]{8,20}$/;

Regex to accept atleast one alphabet one numeric char and one special Character

I was trying to write a regex that accetps a string that has atleast 1 number 1 alphabet and 1 special character ,
/^[a-zA-Z][a-zA-Z][##$%^& .. and a bunch more]+$
But this is not working
You can use lookaheads:
/^(?=.*?[a-z])(?=.*?\d)(?=.*?[...])/i
[...] should hold the special characters you want.
var item = "1a$";
item.match(/^[0-9][a-zA-Z][^a-zA-Z0-9\s\t\n]$/)
That should work
You can use 3 little regex to accomplish that easily (it's more readable) :
[0-9]
[a-zA-Z]
[-_$#...]

Regex to check if field has both numbers and letters

I was just looking for a regex expression to check and see if both numbers and letters exist.
Just to clarify the query, the regex is going to be written in javascript and used to validate an address.
I would use a regular expression which matches any letter followed by any digit (with any possible characters in between) or digit then letter (with anything in between):
var hasNumbersAndLetters = function(str) {
var regex = /(?:[A-Za-z].*?\d|\d.*?[A-Za-z])/;
return !!str.match(regex);
};
Much easier to run two checks.
/\pL/ && /\pN/
To do both checks in one pattern, you need something like
/\pL.*\pN|\pN.*\pL/s
Languages supporting zero-width lookaheads can eliminate the redundancy:
/^(?=.*\pL/)(?=.*\pN/)/s ( or /^(?=.*\pL/).*\pN/s )
But it's harder to read.
Pardon me for not using JS's match function, but the question is really about regular expressions, and I'm not familiar with JS's match function.
if it is a single word you are matching without spaces, with both numbers and letters, it can be assumed they touch somewhere - so if it matches letter then number or number then letter we have a match - so:
([a-zA-Z][0-9]|[0-9][a-zA-Z])
Edit: where there may be spaces then you can use lookahead assertions like this
([a-zA-Z](?=.*[0-9])|[0-9](?=.*[a-zA-Z]))
Saw you wanted to validate an address
Removed by regex answer as javascript has no Unicode support, except for matching single characters http://www.regular-expressions.info/unicode.html
This should do it:
^[\w]*[^\W_][\w]*$

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