Regex allow empty string javascript. ^a*|b*$ matches either ^a*; or b*$; i.

Regex allow empty string javascript It's like how the empty set is a subset of every set. if there's {0} of them (an empty string) or | it will match 6 or more {6,} by specifying a range with only the "from" index, a comma, and no "to" index. 01 +2. How does it allow empty strings, could you please elaborate? – Jul 12, 2013 · As others said, you probably mean ^\s*$, not ^\s+$, because ^\s+$ will fail to match the empty string, . But that doesn't do what you think. Feb 28, 2014 · You cannot check for not-null using a regular expression, because that regex is run against the String. How to do it? Jul 7, 2014 · @Mortaza: Regular expressions are often written with forward slashes as delimiters. If you want to match the entire string where you want to match everything but certain strings you can do it like this: ^(?!(red|green|blue)$). That is, there is no way you can make, for instance, Matcher. Also the expression should allow scandinavian letters, Ä,Ö and so on, both lower and uppercase. You could write it like so: [a&&b Jul 23, 2020 · A neat regex for finding out whether a given torrent name is a series or a movie. Thanks in advance @SexyMF: Be aware that your regex is not anchored, it matches blah blahwww. 6 (High Sierra) for 18 chosen solutions. Performance. I want to exclude this possibility. match numbers. Apr 7, 2021 · Regular Expression: Allow letters, numbers, and spaces (with at least one letter not number) 3 Javascript Regex to remove any spaces, special characters and numbers Jun 2, 2016 · @Phoenix The regular expression is correct, but depending on the language you might have to remove the backslash or escape it another time. Regular expressions are used in many programming languages, and JavaScript's syntax is inspired by Perl. You also need to repeat your character class as explained in the answer by Andy E: Jul 27, 2012 · Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand Jan 24, 2025 · A regular expression (regex for short) allow developers to match strings against a pattern, extract submatch information, or simply test if the string conforms to that pattern. Feb 12, 2014 · I'm trying to write a regular expression to remove white spaces from just the beginning of the word, not after, and only a single space after the word. Oct 30, 2012 · You should allow all characters, then filter out the numbers in a second step, using something like result = subject. trim() == '' is saying "Is this string, ignoring space, empty?". test (i. This eliminates only trailing or leading whitespace. Explanation: Using string. The caret (^) and dollar sign ($) metacharacters match the start of a string and its end, respectively. I don't think so. 000001 1. Nov 30, 2012 · @Richard I just tested this on several engines and it seems the simplest approach. May 23, 2011 · The value of separator may be an empty String, an empty regular expression, or a regular expression that can match an empty String. By using that textbox, the user only can key in numeric. 3 And wrong examples: 0001. For example, it should allow 10. Unlike ^$, it will also match a string consistening of only whitespace characters like spaces and tabs, such as May 23, 2017 · There are a lot of pattern types that can match empty strings. The regex must only match the first character for negation. Any help would Jan 12, 2015 · @MadPhysicist TLDR; Yes. See my DEMO above for uses of regex Jul 27, 2010 · To make any pattern that matches an entire string optional, i. *$ This says, start the match from the beginning of the string where it cannot start and end with red, green, or blue and match anything else to the end of the string. Allow empty string with regex. (. /abc/. Second, if you pass a string to the replace function, it will only replace the first instance it encounters. For a regex search-and-replace, use /NT1\// instead of "NT1\/". Nov 17, 2020 · check if string is null or empty java; regex for check if string is only empty or whitespace javascript; c++ check if string is empty; regex is empty string javascript; golang check if string is empty; js if string not empty; check if a string is empty java; python check if string is empty; check if string is empty; typescript check if string May 23, 2017 · if you use javascript for the regex, If you want to also match an empty string, wrap the pattern with an optional non-capturing group: Regex - only allow a Mar 8, 2010 · Matching Anything but Given Strings. Dec 30, 2009 · [. Aug 6, 2010 · If you want the pattern to match the null-string, the answer is that it's impossible. \d{1,3})?$ I want to also match on an empty string "" which i believe is ^$ How can I combine these into 1 regex. If you would instead like to match ANY white space (tabs, etc. For example if I enter strings such as "This is a test" or "testing", the regular expression should pass validation. I've tried ^[0-9]{0|9} but obviously that doesnt work. 000 . It's also used extensively as a regex for covering exactly this case (match a string non-empty, non-whitespace) in e. Jun 29, 2015 · The regular expression ends in /ug. isEmpty() Feb 18, 2016 · I've found this beautiful method for removing empty strings - arr = arr. 000 123456789 0 . The hyphen is being treated as a range marker -- when it sees ,-! it thinks you're asking for a range all characters in the charset that fall between , and ! (ie the same way that A-Z works. 2 days ago · However, using trim() on a string that is only whitespace will result in a string that is 0 characters long ‑ meaning that if we pair it with the length property, we end up with a neat and lightweight way to detect strings that are only whitespace. 0. Learn more Explore Teams Dec 15, 2010 · I need a Java regular expression, which checks that the given String is not Empty. I have everything working fine but empty string. From the MDN Docs , the function returns -1 if there is no match. has no special meaning inside of [], it just means a literal . Aug 22, 2013 · You may want to try wrapping your expression in the following ^\s*(expression)\s*$. alphanum() makes your check ignore whitespace. 5 Regular Expression Literals NOTE Regular expression literals may not be empty; instead of representing an empty regular expression literal, the characters // start a single-line comment. Suppose you already have a framework in place that tokenizes by running through a list of regular expressions. Instead of ^$, you can match ^\s*$, that is read as "match the beginning of the string, followed by zero or more whitespaces, and the end of the string". But it doesn't seem to work on whitespace strings. Javascript regular expression should allows empty and non-empty string, but it doesn't Empty String Match In Regular Expression. Invesion of regular language is the regular language. \n] does not work because . Here's the code: console. Also, when you define a regex using a constructor notation, you are using a string literal where backslashes are used to form string escape sequences and thus need doubling to form regex escape sequences. * -> Quantifier, Matches between 0 and unlimited. Since this regex is matching everything from the start of the string (^) to the end of the string ($), a match() here will return the whole string or null. We‘ll study code examples for each technique, compare the pros and cons, and look at some sample use cases where these concepts come into play. e. I perform tests on macOS v10. any character except newline \w \d \s: word, digit, whitespace \W \D \S: not word, digit, whitespace [abc] any of a, b, or c [^abc] not a, b, or c Mar 11, 2015 · I have regex: ^[a-zA-Z0-9,. You're also not guaranteed for trim to be defined via a regex, a lot of JS engines have it built-in. If you're using some plugin which takes string and use construct Regex to create Regex Object i:e new RegExp() Than Below string will work '^\\S*$' It's same regex @Bergi mentioned just the string version for new RegExp constructor Dec 1, 2011 · I've a regular expression that allows a string to be empty. replace() to a variable because it returns a new string. May 29, 2023 · I am searching for a regular expression for allowing alphanumeric characters, -, _ or spaces in JavaScript/jQuery. If it's empty "word" is only composed by whitespaces: If it's empty "word" is only composed by whitespaces: Just read your regex from left to right: what it really means is not "match the beginning and the end of the string", but "match the beginning of the string, then the end of the string". sub(regular_expression, '', old_string) re substring is an alternative to the replace command but the key here is the regular expression. search() if you're only interested in a boolean value. Check Wikipedia for a brief history of how this came into existence. To match a string if it only consists of alphanumerics or is empty use ^[a-zA-Z0-9]*$ See the Oct 27, 2016 · I have done my regular expression in JavaScript and my regex allows alpha characters, numbers, space and empty string. Reason: People have all kinds of ways to enter phone numbers ( 1-(123) 343-2345 etc. But iam trying to allow null also to this , but could not. ), you can use \s* instead of * , making the regex the following: Jul 23, 2022 · From a theoretical perspective, the empty regex describes the empty language. filter(Boolean). By Negative Lookaheads. 00 1. I assume you also need to be able to match empty strings (the original regex matches empty strings). – Jun 14, 2013 · Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand Aug 22, 2018 · |has very low precedence. I want to not allow the placement of links. matches() return true for a null input string. I want null or empty to be accepted. g. 2 -12 -1. Also, you mentioned a null string. Aug 12, 2022 · I'm currently using this regex ^[A-Z0-9 _]*$ to accept letters, numbers, spaces and underscores. (You can also use new RegExp()). But the string containing whitespace(s) in the middle CAN match. 2. The string should ONLY have a-z, A-Z, 0-9, _ (underscore), . So it matches both the previous condition (zero Mar 18, 2019 · The . prototype. Feb 15, 2012 · This will work too, it will accept only the letters and space without any symbols and numbers. grep --invert-match Apr 20, 2021 · This regular expression ^\w+(\s\w+)*$ will only allow a single space between words and no leading or trailing spaces. This removes the whitespace in the beginning but allows space at the end. The /s _italic_means ANY ONE space/non-space character. \-]/g, '') is a good start, but allows subtraction formulas, such as -7-8, which will break data systems without server side checking. Using Anchors. blah. With Positive Lookaheads. It should allow only up to two decimal places. This RegExp should do this j Nov 14, 2013 · I would like to have a regex which matches the string with NO whitespace(s) at the beginning. But it may not start or end with a space. Here's how: Method 1: Using Regex. Currently, I am using this RegExp - Apr 5, 2012 · I want a regex in JavaScript for validating decimal numbers. 3 EDIT: standart JavaScript regex. See the regex demo. com another comment is avoid capture groups when yoou don't need to capture, prefer non capture group. 0 1. Apr 24, 2019 · It converts the string into an array of single-character strings via a spare method, and then applies filter function over JavaScript on each array item, returning a new string array, to finally join that array back into a string. A proper explanation would greatly improve its educational value by showing why this is a good solution to the problem, and would make it more useful to future readers with similar, but not identical, questions. For example, if you use / (most common) then it should be escaped inside the character class above by adding a back-slash before, like this: \/. Yes, the regex is simple, but it's still less clear. In short: right at the start of the string, we check the whole string for just zeros. 899. replace() doesn’t change the string itself, it returns a changed string. It should also allow only one perio Oct 2, 2013 · That's a post about a regex which doesn't match the empty string with a set of answers as to why. But not start with 0. , one that will not match anything. Sep 27, 2016 · $ - end of string. Saying foo. Regular expression - also empty string allowed. If you want to match all newlines, you would need to add \r as well to include Windows and classic Mac OS style line endings: (. I could of course replace * with +, but that would exclude the empty string. Syntax is fine. 1 1. 3. Here is the regex for the date; is there any way to put "or empty" into this also: Dec 2, 2018 · I need regular expression to not allow only whitespaces in a field(the user should not enter just whitespaces in the field) but it can allow completely empty field and it can also allow string with whitespaces in between. Cursor position: beginning of test string: before char 1: a. See this SO question and this blog post for discussion and more details. Logically, an empty regular expression should match strings containing "emptiness" at any position--which of course is all of them. Let‘s dive in! Aug 25, 2024 · A simple way to match empty strings is by using the start ^ and end $ anchors, with nothing between them: /^$/ This matches: ‘‘ // empty string. NET. also, I have to restrict some special characters at the beginning of the string. Several languages, including JavaScript, use the same delimiter notation. 000 I hope I have covered all of them. ^ denotes the start, $ the end of the string. When you're using a group, you're getting: Aug 16, 2017 · You seem to need to avoid matching strings that only consist of digits and make sure the strings start with an alphanumeric. Details ^ - start of string (?!\s+$) - a negative lookahead that fails the match if there are 1 or more whitespaces and end of string immediately to the right of the current location Regular expression tester with syntax highlighting, explanation, cheat sheet for PHP/PCRE, Python, GO, JavaScript, Java, C#/. It allows for empty inputs, multiple emails separated by ; which comply with the RFC for majority usage of email addresses. Nov 18, 2011 · [^+]means "match any single character that is not a +" [^+]* means "match any number of characters that are not a +" - which almost seems like what I think you want, except that it will match zero characters if the first character (or even all of the characters) are +. Apr 30, 2013 · The regex ^$ matches only empty strings (i. Oct 28, 2024 · This page provides an overall cheat sheet of all the capabilities of RegExp syntax by aggregating the content of the articles in the RegExp guide. When match something, mathc all the string with the exception of the eventually space at the and Submitted by Luca - 10 years ago Apr 19, 2016 · Your ^$|[a-zA-Z0-9] matches an empty string with ^$ or (|) an alphanumeric character (with [a-zA-Z0-9]). 89 but not 10. either a string beginning with 0 or more 'a's or a string ending with 0 or more 'b's. Below is the explanation of the regular expression: ^ Assert position at start of the string \w+ Match any word character [a-zA-Z0-9_] Quantifier: + Between one and unlimited times, as many times as possible, giving back as A string with only spaces or no characters is an empty-string. I've checked several questions on Stack and the Joi docs without bein Jan 22, 2013 · For a project, I'm trying to develop a regex that takes either A) an empty string (in C# speak, ""), or B) ten (10) digits. Solutions works slightly different (for corner-case input data) which was presented in the snippet below. Dec 8, 2015 · I'm trying to check if there's a number in a text input using regular expression. Sep 4, 2016 · Another advantage of pre-checking for empty/null strings is that you can reuse the same regular expression for validating in other parts of your code, where you don't want to allow such user names. wazuh. +[^\s]$ Any string that doesn't begin or end with a white-space will be matched. var arr = ['Apple If using this regex, you should also escape your regex delimiter. 56. Whether ^\s*$ matches an empty string depends on your definition of "empty". i would like the same regular expression in ColdFusion. It's extremely ugly and long and complicated and your regex parser probably can't handle it anyway. Regex to allow only alphanumeric and empty strings. If you need to check if a string contains only whitespaces, you can use ^\s*$. For example, /re/ is used for the regular expression re. Since I need it inside the function that handles the change of a numeric field and in order to add a negative value the user firstly adds the "-" or deletes the old value (""), I need to match all these 3 conditions. Jan 22, 2014 · Javascript regular expression should allows empty and non-empty string, but it doesn't Regular expression - also empty string allowed. 123 0. Mar 24, 2023 · How to Use JavaScript Regex to Check if a String is Empty If you are a web developer, you have probably come across the need to check if a string is empty. Sep 13, 2021 · Regex for allow some special characters but not allowing spaces in javascript? 1 regex to allow space and restrict special characters at the beginning of a non empty string Apr 4, 2010 · Learn how to use JavaScript regular expressions to replace non-numeric characters in a string. com$*!§?#~´&² for example, and the dot in (http(s)?:\/\/. That is why I suggest ^(?!\d+$)(?:[a-zA-Z0-9][a-zA-Z0-9 @&$]*)?$ See the regex demo. How can I make it log "good" when there isn't anything in the text input? Mar 31, 2023 · In this article, I’ll show you three ways to match an empty string in RegEx. Jul 14, 2010 · Are you trying to check to see if a string is empty? (as in only has whitespace) If so ^\w*$ would match such a string. Regex pattern and test string, for reference: x* Matches between zero and unlimited times, as many times as possible, giving back as needed (greedy) abxd. So, if you don’t put anything between both ^ and $, it matches an empty string: In this comprehensive guide, you‘ll learn three methods for matching empty strings in JavaScript regular expressions: 1. domain. Aug 16, 2016 · How about NOT checking "word" by RegExp but using RegExp to replace all whitespaces and look what's left. strings of length 0). but will not accept an empty string. I really tried and couldn't find a post about a regex which only matched an empty string, let alone one which dealt with that and the difference between \z and \Z. |[\r\n]). I think regular expression library in what you leverage - should support it, but if not you always can write your own library. Returns the full name of the series with the separator needed to make it pretty (ie, replace it with space or what you want). Note that \d matches also digits from other character sets like ٠١٢٣٤٥٦٧٨٩. Also, note that you have to assign the result of the . However the expression should ingnore if the user has accidentally given whitespace in the beginning of the input, but allow whitespaces later on. Like ^$, it will match the completely empty string . First, String. I've been able to figure out how to Jun 5, 2019 · This RegEx will allow neither white-space at the beginning nor at the end of your string/word. (Because matching 0 'a's is allowed by the regex, any string will match (because every string has a beginning). – Oct 16, 2016 · The following expression will match the whole string ^ $ for any character . May 26, 2017 · I need a regular expression allow comma after a Any commas at the start should be replaced with an empty string '' javascript regular expression, allow only May 15, 2012 · The pure regex way of doing this would be [A-TVWZ]|^$ which will either match one of the aforementioned letters or the empty string. Nov 27, 2017 · You shouldn't use String. Here ^ and $ are the beginning and end of the string anchors, respectively. Together they ensure that the whole string is matched. *$ type, and it is easy to modify it to prevent empty string matching by replacing * (= {0,}) quantifier (meaning zero or more) with the + (= {1,}) quantifier (meaning one or more), as has already been mentioned in the posts here. please help One option is the empty regular expression, denoted in JavaScript as /(?:)/. ^a*|b*$ matches either ^a*; or b*$; i. Nov 15, 2011 · This will allow "silly" numbers like 007 as well, but not 0 or 000 or an empty string. log("number"); console. 00 . If you don't use a regular expression for numbers, you have to write a special case for it: iterate through the list of regular expressions and then also check with jQuery whether the token is numeric. That’s why I passed a regular expression with the g flag, for 'global', so that all instances will be replaced. Jul 30, 2015 · Thank you for this code snippet, which may provide some immediate help. ) Jul 23, 2012 · this string will return true for alphabets, numbers and ,-_. ), and they don't like it if a website tells them the number is incorrect. Used RegExp: var re = new RegExp(/^([a-zA-Z The / starting and ending the regular expression signify that it's a regular expression. If you need more information on a specific topic, please follow the link on the corresponding heading to access the full article or head to the guide. Oct 16, 2019 · returns true if the string is valid; returns false if the string contains an invalid pattern; Then we iterate over the string using split and reduce, and let's decide what to accept or to reject, char by char: May 8, 2012 · I am trying to explode an string using javascript to pick searchterms, whitespace-separated. So far i have tried below [^-\\s][a-zA Jun 2, 2017 · The question does not mention if empty string is valid or not , so read this carefully by OP I am planning to match a string against the allowed pattern. I'm using yup and formik with react and typescript. Aug 8, 2017 · Check if the string is empty or not using the following regex: The regex above matches the start of the string ( ^ ), then any number of spaces ( * ), then the end of the string ( $ ). Nov 7, 2017 · To allow an empty string match, wrap the whole pattern with an optional non-capturing group: JavaScript RegEx to allow only AlphaNumeric Characters and some Apr 7, 2016 · Iam using below regular expression currently in XSD as below <xs:pattern value="[A-Z]{3}"/> This is working fine for alphabets. ) matches any character between the double slash and the url, for example https://{subdomain. 0 . i tried putting [null]|[A-Z]{3} but this is also not accepting null. The ^ means italic NOT ONE of the character contained between the brackets. 13. Regex takes a string and returns a string and the processing is done via native code. |\n) would be a way to specify "any character, including a newline". (dot) , - (hiphen). See: \d is less efficient than [0-9]. Allow empty string Jan 7, 2014 · Javascript regular expression should allows empty and non-empty string, but it doesn't. These should be the passing tests "" //empty string 1 1. The empty language is a sub-language of every other language. Try to find a library routine for matching them. The u turns on unicode support, including the \p notation for specifying entire unicode character classes; and the g indicates global replacement, so that all non-alphanumeric characters found are replaced with the null string instead of just the first. The / at both ends mark the start and end of the regex; The ^ and $ at the ends is to check the full string than for partial matches \d* looks for multiple occurrences of number charcters; You do not need to check for both \d as well as [0-9] as they both do the same - i. + -> Quantifier, Matches between 1 and unlimited. Oct 23, 2019 · Create "regular expression to detect empty string", and then inverse it. 23234 123. Javascript : Empty String Match In Regular Expression. replace(/\D+/g, "");. How can I do it so that a -must be followed by at least one number, but a completely empty string is still OK? Jan 2, 2014 · The | in your regex allows it to match either of these two possibilities: ^[a-zA-Z]{2}[\d]{7} [\d]{10}$ That is, start of string then 2 letters and seven numbers followed by anything, or anything followed by 10 numbers and end of string. See this answer for an example. Oct 10, 2022 · I'm in the process of creating a regex expression that removes spaces in the beginning and end. – Note that you need the g flag on the regular expression to get replace to replace all the newlines with a space rather than just the first one. Nov 11, 2021 · Javascript 2022-03-27 22:25:20 javascript download string as file string regular expression do not allow empty string empty Moshen, replace(/[^0-9. By the way, if this is Javascript, you are doing a literal string replacement. Your comment indicates that the user can only enter a single character anyway, so another option would be @rps. However I get empty array elements if a searchterm is ended by a whitespace, as shown below. after the user key in the 1-9 at the first character, the May 13, 2020 · The last third, fourth and fifth match a string that contains at least one non-whitespace char. Since there is nothing in-between, this regex can only accept (= match) empty strings. The requirement is to allow spaces at the beginning of a string if the string is non-empty. allow a pattern match an empty string, use an optional group: ^(pattern)?$ ^^ ^^^ See the regex demo Character classes. It does not modify the existing string. This can be done using JavaScript and Regex. And I'm doing it inside an Angular Directive. – Jan 4, 2018 · I have used this regex: ^(-?)[\d]*$ It works well, but it also accepts only the minus character alone '-' . Jan 23, 2022 · import re regular_expression = r'[^a-zA-Z0-9\s]' new_string = re. ^[a-zA-z\s]+$ ^ asserts position at start of the string Match a single character present in the list below [a-zA-z\s] Mar 31, 2016 · First of all this question is not same as strip non-numeric characters from string or Regex to replace everything except numbers and a decimal point I want to convert a string with valid number Jan 16, 2018 · Javascript Regex: Match any non-word character that is not a whitespace character 1 regex to allow space and restrict special characters at the beginning of a non empty string Jul 8, 2020 · I need a regex that would match a positive and negative decimal value, empty string ('') and also minus only ('-'). I need to modify it to require at least one number or letter somewhere in the string. Here is my JavaScript: /^([A-Z0-9 ]{1,50})?$/i and here is what I have in ColdFusion: Sep 23, 2013 · That regex means either: ^\d{4} OR $ The first will match just any string that starts with 4 digits while the second will report a match on everything (it matches the end of a string, and since no character is specified, it will match the end of all strings). Depending on what method/language you are using that regex it can fetch different results. test("abcd")) instead of String. log("bad"); It works well, but if I add text, then backspace all the way, I get "bad". For example: 10 0. match but RegExp. If it isn't empty the string may contain only letters and spaces. Sep 22, 2009 · When the user hits submit it shows a warning on the date input field since the empty string does not match the validation of a date. But does NOT match: ‘ ‘ // space only ‘\n‘ // newline only ‘ \t‘ // spaces and tabs Apr 21, 2024 · The first way to match an empty string with a regular expression is to use the start and end anchors (^ and $) with nothing in between them. ]*$ but I want to allow only one dot in string. *\d)[\p{L}'-]+$ Jan 3, 2013 · I have a textbox that I created using . match(/^\s*$/) is asking "Does the string foo match the state machine defined by the regex?". To check the String isn't empty you can just use !myString. I need some way to say that nothing or a date is valid in a regex. Oct 30, 2013 · I have this javascript Regex (3 decimal places wiht a single dot) ^\d+(\. Then use the groups to find the "trimmed" matches. ^[^\s]. I suggest you to read on Character Classes. Jun 29, 2023 · Only allow the special characters -and ' Spaces should not be allowed at the beginning or end of the field; Remove any additional blank space if found between parts of names (allow only one space between parts of name - if multiple middle names) Allow diacritics; Chat GPT gave the following: ^(?!. match(regex) will return null if there are no matches otherwise it returns an array of matched strings. test() The easiest way Mar 10, 2016 · I ended up using string. What you have to modify it's the last part. 1. This is how you would use it: "String!! Think of Regex like a cursor in a word processor. Feb 21, 2011 · Don't match an email with a regex. the I shape that sits between characters (instead of the _ when using a terminal). Jul 14, 2021 · I want to create a RegExp in javascript. It is possible to write a regex that is the opposite of the empty set, i. This creates a pattern that matches a string with no characters – an empty string. split(;) and then passing through an improved RegEx which should account for 99% of email addresses in use today. start with 1-9. And from 7. 8. . The search function takes both strings and regexes, so the / are necessary to specify a regex. Here is what I have so far: /^[^\s][a-zA-Z0-9][a-zA-Z0-9-_]*$. NOTE: To also allow empty value, use 0 as the min argument in the limiting quantifier: ^(?!0+$)[0-9]{0,10}$ ^ See How Negative Lookahead Works to learn more about how (?!0+) works in this pattern. The current regex im using is: ^[0-9]{9} Which works if the field is mandatory, however we have a new requirement that this can also be empty. NET, Rust. The regular expression is a union, created by the Apr 18, 2012 · Hi I am having trouble trying to create a regex that will allow me to have the field empty or a string with length 9 if populated. The OP regex belongs to an ^. – Apr 11, 2013 · Or – | – match the beginning of the string followed by the end of the string – ^$ –. Depending on what language you're using, passing a NULL pointer to a regex function may result in a segfault. A character class matches just a single character, from all the characters included in it. I'm guessing the above logic is to be used in some UI code, where the user is still entering the data; you might want to ensure that the username May 24, 2022 · I would like my Joi middleware to keep the alphanum() validation but also allow empty spaces in both event_name and venue_name. Jan 26, 2019 · Regex allow empty string. Details ^ - start of string Jul 2, 2013 · Now available on Stack Overflow for Teams! AI features where you work: search, IDE, and chat. grpv jsxcmbq jqrp hwpa qlfe brmvr ifwwthx typnyr jxyo qghdhz gnmd joffy wvacokm wluk fhevyknt