Email validation and Trim javascript functions

function LTrim( value ) {

var re = /\s*((\S+\s*)*)/;
return value.replace(re, "$1");

}

// Removes ending whitespaces
function RTrim( value ) {

var re = /((\s*\S+)*)\s*/;
return value.replace(re, "$1");

}

// Removes leading and ending whitespaces
function trim( value ) {

return LTrim(RTrim(value));

}

function Emailcheck()
{
var common = 'ctl00_ContentPlaceHolder1_ctl03_';
var wholestring = document.getElementById(common+'txtMerchantEmail').value;
var lblErrorPersonalInfo = document.getElementById(common+"lblErrorPersonalInfo");
var splitChar;
splitChar=";";

var col_array=wholestring.split(splitChar);
var part_num=0;
while (part_num < col_array.length)
{
var trimedString = trim(col_array[part_num]);
if(trimedString.search(/^\w+((-\w+)|(\.\w+))*\@[A-Za-z0-9]+((\.|-)[A-Za-z0-9]+)*\.[A-Za-z0-9]+$/)=="-1")
{ lblErrorPersonalInfo.innerHTML ="Either the email addresses are not ';' separated or one or more email addresses are not valid.";

return false;
break;
}
part_num+=1;
}

return true;

}

Is Dirty page Implementation : javascript

window.onbeforeunload = function (oEvent)
{
var isdirty = document.getElementById("ctl00_IsDirty");
if(isdirty.value=="false")
{

}
else
{
if(!oEvent) oEvent = window.event;
oEvent.returnValue = 'ALL your recent changes will be LOST unless your click CANCEL.';
UnsetDirty();
}

}
function UnsetDirty()
{
var isdirty = document.getElementById("ctl00_IsDirty");
isdirty.value = false;

}
function SetDirty()
{

var isdirty = document.getElementById("ctl00_IsDirty");
isdirty.value = true;

Validate Date: javascipt

//date check
var dtCh= "/";
var minYear=2003;
var maxYear=2019;

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 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++){
var c = s.charAt(i);
if (bag.indexOf(c) == -1) returnString += c;
}
return returnString;
}

function daysInFebruary (year){
// February has 29 days in any year evenly divisible by four,
// EXCEPT for centurial years which are not also divisible by 400.
return (((year % 4 == 0) && ( (!(year % 100 == 0)) || (year % 400 == 0))) ? 29 : 28 );
}
function DaysArray(n) {
for (var i = 1; i <= n; i++) {
this[i] = 31
if (i==4 || i==6 || i==9 || i==11) {this[i] = 30}
if (i==2) {this[i] = 29}
}
return this
}

function isDate(dtStr){

var daysInMonth = DaysArray(12)
var pos1=dtStr.indexOf(dtCh)
var pos2=dtStr.indexOf(dtCh,pos1+1)
var strMonth=dtStr.substring(0,pos1)
var strDay=dtStr.substring(pos1+1,pos2)
var strYear=dtStr.substring(pos2+1)
strYr=strYear;
if (strDay.charAt(0)=="0" && strDay.length>1) strDay=strDay.substring(1)
if (strMonth.charAt(0)=="0" && strMonth.length>1) strMonth=strMonth.substring(1)
for (var i = 1; i <= 3; i++) {
if (strYr.charAt(0)=="0" && strYr.length>1) strYr=strYr.substring(1)
}
month=parseInt(strMonth);
day=parseInt(strDay);
year=parseInt(strYr);
if (pos1==-1 || pos2==-1){
alert("The date format should be : mm/dd/yyyy");
return false;
}
if (strMonth.length<1 || month<1 || month>12){
alert("Please enter a valid month");
return false;
}
if (strDay.length<1 || day<1 || day>31 || (month==2 && day>daysInFebruary(year)) || day > daysInMonth[month]){
alert("Please enter a valid day");
return false;
}
if (strYear.length != 4 || year==0 || yearmaxYear){
alert("Please enter a valid 4 digit year between "+minYear+" and "+maxYear);
return false;
}
if (dtStr.indexOf(dtCh,pos2+1)!=-1 || isInteger(stripCharsInBag(dtStr, dtCh))==false){
alert("Please enter a valid date");
return false;
}
return true
}

Javascipt Timer

This javascript is for creating a timer on a page using setTimeout method.
you can modify the end condition by removing _PostBack("A", "B") part incase you dont want postback at the end of the time.
var milisec=0
var seconds = 20
var flag = 1


function display(){
if (milisec<=0){
milisec=9
seconds-=1
}
if (seconds<=-1){
milisec=0
seconds+=1
}
else
milisec-=1
document.getElementById("lblTimer").innerHTML=seconds

if (seconds <= 0 && flag == 1) {
flag = 0;
__doPostBack("A", "B");
}
setTimeout("display()",100)
}