Dynamic phonenumber formatting in Javascript. It is implemented only for US/Canada, and others as international.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>
<head>
<title>Untitled</title>
</head>

<body>
<form>
<input name="a1" type="text" value="" onkeyup="javascript:keyUP(this,event);" onblur="javascript:validatePhone(this);">
</form>

</body>
<SCRIPT LANGUAGE="javascript">
function keyUP(object, e) {
if (e) {
e = e
} else {
e = window.event
}
if (e.which) {
var keycode = e.which
} else {
var keycode = e.keyCode
}

if (keycode >= 48) {
ProcessString(object)
}

}

function ProcessString(object) {

validatePhone(object);
}

function validatePhone(obj) {
var phoneStr = obj.value;
phoneStr = phoneStr.replace(/^\s+|\s+$/g, '');
var testArr = phoneStr.split("");
var j = 0;
var arraySize = testArr.length;
var keychar = testArr[0];

if (keychar == "+") //international format
{
for (i = 1; i < testArr.length; i++) {
var testchar = testArr[i];
var newchar = "";
var remchar = -1;
 //alert("test:"+testchar);
var ioffset = 0;
ioffset = PhoneFormat_International(i, newchar, remchar, testchar, testArr);

i += ioffset;

j++; //to avoid any infinite loop..
if (j == 300) {
break;
}
}
}
else {
for (i = 0; i < testArr.length; i++) {
var testchar = testArr[i];
var newchar = "";
var remchar = -1;
 //alert("test:"+testchar);
var ioffset = 0;
var arrsize1 = testArr.length
ioffset = PhoneFormat_USCanada(i, newchar, remchar, testchar, testArr);

i += ioffset;

j++; //to avoid any infinite loop..
if (j == 300) {
break;
}
}
}

obj.value = testArr.join("");

}

function PhoneFormat_USCanada(i, newchar, remchar, testchar, testArr) {
var ret = 0;
if (i > 13) {
testArr.splice(i, 1);
ret = -1;
return ret;
}

switch (i) {
case 0:
if (testchar != "(") {
newchar = "(";
}
else {
remchar = 0;
}
break;
case 4:
if (testchar != ")") {
newchar = ")";
}
else {
remchar = 0;
}
break;
case 5:

if (testchar != ' ') {
newchar = ' ';
}
else {
remchar = 0;
}
break;
case 9:
if (testchar != "-") {
newchar = "-";
}
else {
remchar = 0;
}
break;

default:
if (isNaN(testchar) && testchar != ' ')
remchar = 1;

}

if (remchar != 0 && (isNaN(testchar) || testchar == ' '))

{ remchar = 1; }
 else
{ remchar = 0; }

if (newchar.length > 0) //char to be concatenated for the phone number format
{
testArr.splice(i, remchar, newchar); //if remchar=1, the character is invalid and remove it while
adding a char
}
else if (remchar == 1) //if 1, the character is invalid and remove it
{
testArr.splice(i, remchar);
ret = -1; //only deletion, the same index char needs to be examined
}
return ret;
}

function PhoneFormat_International(i, newchar, remchar, testchar, testArr) {
var ret = 0;
remchar = 1;
if (!isNaN(testchar)) {
remchar = 0;
}
else if (testchar == " ") {

remchar = 0;

} else if (testchar == "-") {
remchar = 0;
}

if (remchar == 1) //if 1, the character is invalid and remove it

{ testArr.splice(i, remchar); ret = -1; //only deletion, the same index char needs to be examined
}
return ret;
}

</SCRIPT>
</html>