Phone Number Validation

Javascript Phone Number Validation

International Phone No. Validation in Forms

In forms when asking for phone numbers fields it is a good idea to use client side validation along with your programming language validation. The following example shows how you can validate an International Phone number in your forms using Javascript.

International Phone Number Format

Most telephone networks nowadays are interconnected in the international telephone network, where the format of telephone numbers is standardized by ITU-T in the recommendation E.164, which specifies that the entire number should be 15 digits or shorter, and begin with a country prefix followed by an area code or city code and the subscriber number, which might consist of the code for a particular telephone exchange. In writing an international telephone number should start with a plus sign ("+") and the country code.the The "+" stands for the international call prefix chosen by the country the call is being made from. The general standard is 00 and this has been implemented by a large number of countries. For North American Numbering Plan (NANP) countries (including the United States and Canada) the call prefix is "011" for other countries and "1" for countries inside the NANP. Click here for NANP phone number validation and US only phone number validation.

Example

Example of Phone Validation

View Explanation of the Code

Cut and Paste Code

Cut 'n' paste code for the above Example

JavaScript Code

/**

* DHTML phone number validation script. Courtesy of SmartWebby.com (http://www.smartwebby.com/dhtml/)

// Declaring required variables

var digits = "0123456789";

// non-digit characters which are allowed in phone numbers

var phoneNumberDelimiters = "()- ";

// characters which are allowed in international phone numbers

// (a leading + is OK)

var validWorldPhoneChars = phoneNumberDelimiters + "+";

// Minimum no of digits in an international phone no.

var minDigitsInIPhoneNumber = 10;

function isInteger(s)

{   var i;

for (i = 0; i < s.length; i++)

{

// Check that current character is number.

var c = s.charAt(i);

if (((c < "0") || (c > "9"))) return false;

}

// All characters are numbers.

return true;

}

function trim(s)

{   var i;

var returnString = "";

// Search through string's characters one by one.

// If character is not a whitespace, append to returnString.

for (i = 0; i < s.length; i++)

{

// Check that current character isn't whitespace.

var c = s.charAt(i);

if (c != " ") returnString += c;

}

return returnString;

}

function stripCharsInBag(s, bag)

{   var i;

var returnString = "";

// Search through string's characters one by one.

// If character is not in bag, append to returnString.

for (i = 0; i < s.length; i++)

{

// Check that current character isn't whitespace.

var c = s.charAt(i);

if (bag.indexOf(c) == -1) returnString += c;

}

return returnString;

}

function checkInternationalPhone(strPhone){

var bracket=3

strPhone=trim(strPhone)

if(strPhone.indexOf("+")>1) return false

if(strPhone.indexOf("-")!=-1)bracket=bracket+1

if(strPhone.indexOf("(")!=-1 && strPhone.indexOf("(")>bracket)return false

var brchr=strPhone.indexOf("(")

if(strPhone.indexOf("(")!=-1 && strPhone.charAt(brchr+2)!=")")return false

if(strPhone.indexOf("(")==-1 && strPhone.indexOf(")")!=-1)return false

s=stripCharsInBag(strPhone,validWorldPhoneChars);

return (isInteger(s) && s.length >= minDigitsInIPhoneNumber);

}

function ValidateForm(){

var Phone=document.frmSample.txtPhone

if ((Phone.value==null)||(Phone.value=="")){

alert("Please Enter your Phone Number")

Phone.focus()

return false

}

if (checkInternationalPhone(Phone.value)==false){

alert("Please Enter a Valid Phone Number")

Phone.value=""

Phone.focus()

return false

}

return true

}

</script>

HTML Code

Explanation of the Code

The JavaScript has the following main functions:

Function checkInternationalPhone is used to verify if the given value is a possible valid international phone number : This function first removes all non-digit characters which are allowed in phone numbers. These delimiters are declared in the lines (found in the beginning of the code) :

var phoneNumberDelimiters = "()- "
var validWorldPhoneChars = phoneNumberDelimiters + "+"

Now that all valid delimiters are removed we just check if the remaining value is an integer and that it has at least a certain number of digits (given by the variable 'minDigitsInIPhoneNumber').
Function ValidateForm is used to make sure that the phone number field is not blank and that it is a valid phone number on form submission

Phone Number Validation