We Keep Coding

Regex Behaves Differently on HTML Pattern than on an Express Backend

I have the following regex pattern on an HTML input field, which is supposed to hold an email address:
<input type="text" pattern="^\w+([.-]?\w+)*#\w+([.-]?\w+)*(\.\w{2,4})+$" /><br>
I furthermore have the same regex on an Express (JavaScript) backend using the following:
var re-email = new RegExp("^\w+([.-]?\w+)*#\w+([.-]?\w+)*(\.\w{2,4})+$")
if (!re-email.test(email)) {
validation = false
}
Although the regex are exactly the same, a specific test input is evaluated as true on the front-end while as false on the backend.
Why is this?
Solution (found after the initial post):
Instead of using "new RegExp" (which is not working) as above, include the Regex within forward slashes as below (which works).
var re-email = /^\w+([.-]?\w+)#\w+([.-]?\w+)(.\w{2,4})+$/

Probably not the answer you are after (not vue.js specific)...
Email address input validation should usually be completed like so:
<input type="email" name="" value="" required />
Specifying the correct "type" to an input field also adjusts input keyboards on mobile devices to make inputting an email address easier.
Your regular expression is poorly written and leads to "catastrophic backtracking" as well as not actually supporting valid email addresses.
Email address validation is generally complex, see this answer and associated question:
https://stackoverflow.com/a/201378/406712
You can also find the HTML email address validation equivalent regular expression in the HTML spec:
https://html.spec.whatwg.org/multipage/input.html#valid-e-mail-address
Also note you failed to escape the characters in the string, the first instance being the \w which without escaping the \ will appear as simply w.
Escaped the string it more like this:
'/^\\w+([.-]?\\w+)#\\w+([.-]?\\w+)(.\\w{2,4})+$/'

How to find working regex pattern multiple times in single line in javascript?

I want to validate an text input field with javascript regex validation.
Validation that is needed is: Input field should have one or multiple email ids, all ending with semicolon(;).
Thus, correct input would be :
→ user1#xxx.com;
→ user1#xxx.com;user2#xxx.com;
→ user1#xxx.com;user2#xxx.com;user3#xxx.com;
Incorrect input would be
→ user1#xxx.com -------- Semicolon is missing
→ user1#xxx -------- Email Id is invalid
→ user1#xxx.com;user2#xxx.com -------- Semicolon(;) is missing after second email id
This is what I have tried so far which validates only one occurence of regex pattern, but not all occurences in single line.
(^[a-zA-Z0-9.!#$%&'*+\/=?^_`{|}~-]+#[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)+(;)+$)
Regex URL: https://regex101.com/r/4svUQz/2/ [All 4 values in TEST STRING should match, but it is matching only first 2]Also, I have checked below articles, but could not find answer.Regex single-line multiple matchRegex for The Same Pattern Multiple Times in One LineHow to validate an email address in JavaScript

First, for a simpler email regex to understand the principles involved, see How to check for a valid email address?. I will use: [^#]+#[^#]+\.[^#]+ with the recommendation that we also exclude space characters and so, in your particular case requiring a semicolon at the end and allowing multiple email addresses on the line:
^([^#\s]+#[^#\s]+\.[^#\s.]+;)+$
Note that I took the basic regex for an email address and appended ; and then put parentheses () around the entire expression and appended + signifying one or more times.
See Regex Demo
Using your regex, with a slight simplification involving the ; (i.e. removing unnecessary parentheses surrounding it):
^([a-zA-Z0-9.!#$%&'*+\/=?^_`{|}~-]+#[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)+;)+$
See Regex Demo

Validate Japanese Email include special characters

I have an Email below:
anzai-kt#itec.hankyu-hanshin.co.jp
Now i want to validate it but not working.
this is my regex:
$scope.emailParten = /^(([^<>()\[\]\\.,;:\s#"]+(\.[^<>()\[\]\\.,;:\s#"]+)*)|(".+"))#((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;

Use this regular expression:
/^\w+([\.-]?\w+)*#\w+([\.-]?\w+)*(\.\w{2,3})+$/
From: https://www.w3resource.com/javascript/form/email-validation.php
Yours doesn't count "-" as a correct character. Generally validating e-mails is more complex, but this should work for most use cases.
This for example:
very.“(),:;<>[]”.VERY.“very#\\ "very”.unusual#strange.example.com
Is a correct e-mail address, but doesn't get covered by the regular expression in my answer.
If you want to support these weird edge cases try:
/^.+#.+\..+$/
Source: http://codefool.tumblr.com/post/15288874550/list-of-valid-and-invalid-email-addresses

Email validation Javascript RegExp

With this RegExp I can easily check if an email is valid or not:
RegExp(/^([\w-\.]+#([\w-]+\.)+[\w-]{2,4})?$/);
However, this just return true for such addresses:
example#example.com
I also want to accept:
*#example.com
What changes I need to apply on my RegExp?
Thanks in advance

To answer your question literally, you can "augment" your regex:
RegExp(/^([\w.*-]+#([\w-]+\.)+[\w-]{2,4})?$/);
But this is a terrible regex for e-mail validation. Regex is the wrong tool for this. Why do you insist on doing it this way?

A couple of things: to accept *#foo.bar:
var expression = /^([\w-\.*]+#([\w-]+\.)+[\w-]{2,4})?$/;//no need to pass it to the RegExp constructor
But this expression does accept -#-.--, but then again, regex and email aren't all too good a friends. But based on your expression, here's a slightly less unreliable version:
var expression = /^[\w-\.\d*]+#[\w\d]+(\.\w{2,4})$/;
There is an expression that validates all valid types of email addresses, somewhere on the net, though. Look into that, to see why regex validating is almost always going to either exclude valid input or be too forgiving

Checking email addresses is not that straightforward, cf. RFC 822, sec 6.1.
A good list of regexes can be found at http://www.regular-expressions.info/email.html, describing tradeoffs between RFC conformance and practicality.

Validate numbers, parenthesis and spaces only in jQuery validation

I am trying and failing hard in validating a phone number within jQuery validation. All I want is to allow a number like (01660) 888999. Looking around the net I find a million examples but nothing seems to work. Here is my current effort
$.validator.addMethod("phonenumber", function(value) {
var re = new RegExp("/[\d\s()+-]/g");
return re.test(value);
//return value.match("/[\d\s]*$");
}, "Please enter a valid phone number");

Bergi is correct that the way you are constructing the regular expression is wrong.
Another problem is that you are missing anchors and a +:
var re = /^[\d\s()+-]+$/;
Note though that a regular expression based solution will still allow some inputs that aren't valid phone numbers. You can improve your regular expression in many ways, for example you might want to require that there are at least x digits, for example.
There are many rules for what phone numbers are valid and invalid. It is unlikely you could encode all those rules into a regular expression in a maintainable way, so you could try one of these approaches:
Find a library that is able to validate phone numbers (but possibly not regular expression based).
If you need a regular expression, aim for something that is a close approximation to the rules, but doesn't attempt to handle all the special cases. I would suggest trying to write an expression that accepts all valid phone numbers, but doesn't necessarily reject all invalid phone numbers.
You may also want to consider writing test cases for your solution. The tests will also double as a form of documentation of which inputs you wish to accept and reject.

You need to use either a regex literal or a string literal in the RegExp constructor:
var re = /[\d\s()+-]/g;
// or
var re = new RegExp("[\\d\\s()+-]", "g");
See also Creating a Regular Expression.
Apart from that, you would need to use start- and end-of-string anchors to make sure that the regex matches the whole string, not only a part of it, and some repetition modifier to allow more than one character:
var re = /^[\d\s()+-]+$/g;

Another approach may be:
function(value) {
return /^\d+$/.test(value.replace(/[()\s+-]/g,''));
}
and if you want to check for the length of the number too, say it has to be a string with 10 digits:
function(value) {
return /^\d{10}$/.test(value.replace(/[()\s+-]/g,''));
}