Android – Flutter – Validate a phone number using Regex

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In my Flutter mobile app, I am trying to validate a phone number using regex. Below are the conditions.

Phone numbers must contain 10 digits.
In case country code us used, it can be 12 digits. (example country codes: +12, 012)
No space or no characters allowed between digits

In simple terms, here is are the only "valid" phone numbers

0776233475, +94776233475, 094776233475

Below is what I tried, but it do not work.

String _phoneNumberValidator(String value) {
    Pattern pattern =
        r'/^\(?(\d{3})\)?[- ]?(\d{3})[- ]?(\d{4})$/';
    RegExp regex = new RegExp(pattern);
    if (!regex.hasMatch(value))
      return 'Enter Valid Phone Number';
    else
      return null;
  }

How can I solve this?

Best Answer

You could make the first part optional matching either a + or 0 followed by a 9. Then match 10 digits:

^(?:[+0]9)?[0-9]{10}$

^ Start of string
(?:[+0]9)? Optionally match a + or 0 followed by 9
[0-9]{10} Match 10 digits
$ End of string

Regex demo

Related Solutions

Javascript – How to validate an email address in JavaScript

Using regular expressions is probably the best way. You can see a bunch of tests here (taken from chromium)

function validateEmail(email) {
    const 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,}))$/;
    return re.test(String(email).toLowerCase());
}

Here's the example of regular expresion that accepts unicode:

const re = /^(([^<>()[\]\.,;:\s@\"]+(\.[^<>()[\]\.,;:\s@\"]+)*)|(\".+\"))@(([^<>()[\]\.,;:\s@\"]+\.)+[^<>()[\]\.,;:\s@\"]{2,})$/i;

But keep in mind that one should not rely only upon JavaScript validation. JavaScript can easily be disabled. This should be validated on the server side as well.

Here's an example of the above in action:

function validateEmail(email) {
  const 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,}))$/;
  return re.test(email);
}

function validate() {
  const $result = $("#result");
  const email = $("#email").val();
  $result.text("");

  if (validateEmail(email)) {
    $result.text(email + " is valid :)");
    $result.css("color", "green");
  } else {
    $result.text(email + " is not valid :(");
    $result.css("color", "red");
  }
  return false;
}

$("#email").on("input", validate);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<label for=email>Enter an email address:</label>
<input id="email">
<h2 id="result"></h2>

Regex – How to validate phone numbers using regex

Better option... just strip all non-digit characters on input (except 'x' and leading '+' signs), taking care because of the British tendency to write numbers in the non-standard form +44 (0) ... when asked to use the international prefix (in that specific case, you should discard the (0) entirely).

Then, you end up with values like:

 12345678901
 12345678901x1234
 345678901x1234
 12344678901
 12345678901
 12345678901
 12345678901
 +4112345678
 +441234567890

Then when you display, reformat to your hearts content. e.g.

  1 (234) 567-8901
  1 (234) 567-8901 x1234

Best Answer

Related Solutions

Javascript – How to validate an email address in JavaScript

Regex – How to validate phone numbers using regex

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