Regex using Javascript

Question

I am trying to create a function that would remove certain characters from a phone number field. So far I have removed parenthesis, spaces, and hyphens as in (321) 321-4321. Also, I removed dots as in 321.321.4321. Lastly, I have validated when 11 digits and starting with 1 even with punctuation.

The code I input:

function phoneNumber(){
   var number = '(321) 321-4321';
   number = number.replace(/[^\d]/g, '');
   return number;
}

I am now trying to have it return null for certain situations like:

When the number exceeds 11 digits
When letters and/or punctuation are present
When the area code does not start with 2-9
When the exchange code does not start with 2-9.

Any attempt to add a statement invalidates my original function. Can anyone help me I am new to regex, but I need help?

check this tutorial out when you can github.com/zeeshanu/learn-regex — hjm
– hjm, Commented Dec 19, 2017 at 16:09
After the .replace why not just examine number? You know what you have is numeric, check its length and the leading characters. — Alex K.
– Alex K., Commented Dec 19, 2017 at 16:10
When you say you want it to return null when letters or punctuation are present, what exactly do you mean? You existing regex is removing those letters, do you mean that you want to rewrite your expression such that if \D matches anything it fails? — ctwheels
– ctwheels, Commented Dec 19, 2017 at 16:13

beaver · Accepted Answer · 2017-12-22 07:44:03Z

Brief

If I understand correctly, you want:

To remove any non-digit characters from the string
To get numbers that are 11 digits in length (or less)
To ensure the first and fourth digits in the number are in the range 2-9 (so not 0 or 1)

Code

The first regex can use \D instead of [^\d] as they both mean the exact same thing.

The second part can use any of the following methods (and more, but these are probably some of the simplest methods):

Regex and .length

/^[2-9]\d{2}[2-9]/.test(number) && number.length <= 11

var numbers = [
  '(321) 321-4321', 
  '321.321.4321', 
  '123.456.7890',
  '321.123.4567',
  '(321) 321-4321-321'
];

function phoneNumber(number){
   number = number.replace(/\D/g, '');
   if(/^[2-9]\d{2}[2-9]/.test(number) && number.length <= 11) {
     return number;
   }
   return null;
}

numbers.forEach(function(number){
  console.log(phoneNumber(number));
});

charAt, regex and length

!/[01]/.test(number.charAt(0)) && !/[01]/.test(number.charAt(3)) && number.length <= 11

var numbers = [
  '(321) 321-4321', 
  '321.321.4321', 
  '123.456.7890',
  '321.123.4567',
  '(321) 321-4321-321'
];

function phoneNumber(number){
   number = number.replace(/\D/g, '');
   if(!/[01]/.test(number.charAt(0)) && !/[01]/.test(number.charAt(3)) && number.length <= 11) {
     return number;
   }
   return null;
}

numbers.forEach(function(number){
  console.log(phoneNumber(number));
});

Regex (alone)

Obviously, you'd change 0 to whatever your minimum digits requirements are (minus 4); so if you want a minimum of 9, you'd put {5,7}.

/^[2-9]\d\d[2-9]\d{0,7}$/.test(number)

var numbers = [
  '(321) 321-4321', 
  '321.321.4321', 
  '123.456.7890',
  '321.123.4567',
  '(321) 321-4321-321'
];

function phoneNumber(number){
   number = number.replace(/\D/g, '');
   if(/^[2-9]\d\d[2-9]\d{0,7}$/.test(number)) {
     return number;
   }
   return null;
}

numbers.forEach(function(number){
  console.log(phoneNumber(number));
});

Nisal Edu · Accepted Answer · 2017-12-19 16:36:01Z

1

Try as follows use .length to get characters in string

var number = '(321) 321-4321';
number = number.replace(/[^\d]/g, '');
console.log(number)

if (number.length > 11) {
  console.log("null");
} else {
  console.log(number.length);
}


if (number.match(/[a-z]/i)) {
  console.log("alphabet letters found");
} else {
  console.log("alphabet letters not found");
}

edited Dec 19, 2017 at 16:36

answered Dec 19, 2017 at 16:13

Nisal Edu

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Regex using Javascript

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Brief

Code

Regex and .length

charAt, regex and length

Regex (alone)

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