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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})+$/'

Regex not recognizing input value for vehicle license plate

I'm having a problem with my regex validation code. I'm trying to figure out how can I validate a vehicle license plate number. The code that I wrote is listed below this message. This is written down in React inline code and I've written down two different regex expressions and both of the come out to be false. The license plate number should be in this format XX-NNNN-XX.
X = Letter
N = Number
const [licencePlate, setLicencePlate] = useState('');
var ValidateLicencePlate = /^[A-Z][A-Z]-[0-9][0-9][0-9][0-9]-[A-Z][A-Z]$/g ;
var regex = /^[A-Z]{2}-[0-9]{4}-[A-Z]{2}$/g ;
<input name="licence-plate" type="text" className="feedback-input" maxLength='10' onChange={(e) => setLicencePlate(e.target.value.toUpperCase())} placeholder="XX-NNNN-XX"/>

This regex can solve the problem.
let regex = /^[A-Z]{2}-\d{4}-[A-Z]{2}/gi
This regex will match two alphabet at the beginning, four digits at the middle and two alphabet at the end.

You can use regex as following
<input pattern="/^[A-Z]{2}-\d{4}-[A-Z]{2}/g"/>

You can put your regex in the pattern attribute of the input element. I do not see you are using regexps yo have defined anywhere in your listing.
<input pattern={regex}/>
If you have a regex constraint to validate against it may be better and more comfortable to use Constraint Validation API.
<input pattern="your regex here"/>
Browser already validates everything in form elements if you constraint them with various ways like patter attribute and unless you tell it not to validate. But still I see many code bases trying to do the validation themselves. It is unnecessary since there is a way platform itself supports and does itself.

Matching an input pattern beginning of script

I'm trying to match only GitHub URLs with the following input tag:
<input type="url" id="repoUrl" title="Must be a full URL to a GitHub repository" pattern="^https:\/\/github\.com\/" required>
In regex101 this exact pattern is matching all strings that start with "https://github.com" which is what I want, but the problem is that when I call the checkValidity() method on that input, it only says it's valid if the input is only "https://github.com".
What do I need to change to make this regex work how it works in regex101?

try to add .* in the end of a pattern
pattern="^https:\/\/github\.com\/.*"

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

Restrict input some personal information

I want to check what users type in Textarea.
Actually, how can I restrict typing phone numbers and e mail addresses in description box?
So for example:
Hi, I am selling a Bugatti Veyron
Age: 2010
Color: Black
You can contact me on 066/656-656 or 055646646
or via mail mesell#domain.com
If someone tries to enter something like this I want to automatically remove
personal contact details.
So, please help, how can I do it?

Use Regex and do something like this :
Here's an example (jsFiddle)
HTML
<textarea></textarea><br>
<button>Test</button><br>
<span class="result"></span>
Javascript:
function validateEmail(email) {
var re = /^(([^<>()[\]\\.,;:\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,}))$/;
$('.result').html(re.test(email));
if(re.test(email)){
$('.result').html("Contain email");
} else {
$('.result').html("Do not contain email");
}
}
$('button').click(function(){
validateEmail($('textarea').val());
});
Note that I only look for email. But you can use other Regex to look for phone, you just have to search for something like "javascript regex phone" on Google.

you can try Regex as suggested, but take into consideration it's very hard to stop a phone number from being entered(unless you stop ALL numbers or know the exact form of the number taking place).
For example, stopping a xxx-xxxxxxx number is easy, but the user can type each digit with a space after it, which makes it much harder to stop(unless you again remove the option to type numbers.
As for emails, a simple regex to find a # followed by some text, a dot and 2 or 3 characters normally finds emails pretty easily. be advised people can still be creative in the way they put their emails(AT instead of # for example).
this should all be done server side, you can use javascript on the clientside to make it UI friendly.

For email validation:
<input type="email" name="email">
Here is an example: http://www.w3schools.com/html/tryit.asp?filename=tryhtml5_input_type_email
For Phone number validation:
use regex, it should be straight forward though.
Or just try isNAN(value) where value is the phone number enterd, will tell you if this is a number of not and then you can also put a check on number of digits.
Hope this helps!