function trim(s)
{
  return s.replace(/^\s+|\s+$/, '');
}

function validateEmail(fld) 
{
	var error="";
	var tfld = trim(fld.value);                        // value of field with whitespace trimmed off
	
	var emailFilter = /^[^@]+@[^@.]+\.[^@]*\w\w$/ ;
	var illegalChars= /[\(\)\<\>\,\;\:\\\"\[\]]/ ;
   
	if (tfld == "") {
		//fld.style.background = 'Yellow';
		error = "You didn't enter an email address.\n";
		return false;
	} else if (!emailFilter.test(tfld)) {              //test email for illegal characters
		//fld.style.background = 'Yellow';
		error = "Please enter a valid email address.\n";
		return false;
	} else if (tfld.match(illegalChars)) {
		//fld.style.background = 'Yellow';
		error = "The email address contains illegal characters.\n";
		return false;
	} else {
		//fld.style.background = 'White';
		return true;
	}
	//return error;
}


function isEmpty(str)
{
  return (str == null) || (str.length == 0);
}
// returns true if the string is a valid email
function isEmail(str)
{
  if(isEmpty(str)) return false;
  var re = /^[^\s()<>@,;:\/]+@\w[\w\.-]+\.[a-z]{2,}$/i
  return re.test(str);
}
// returns true if the string only contains characters A-Z or a-z
function isAlpha(str)
{
  var re = /[^a-zA-Z]/g
  if (re.test(str)) return false;
  return true;
}
// returns true if the string only contains characters 0-9
function isNumeric(str)
{
  var re = /[\D]/g
  if (re.test(str)) return false;
  return true;
}
// returns true if the string only contains characters A-Z, a-z or 0-9
function isAlphaNumeric(str)
{
  var re = /[^a-zA-Z0-9]/g
  if (re.test(str)) return false;
  return true;
}
// returns true if the string's length equals "len"
function isLength(str, len)
{
  return str.length == len;
}
// returns true if the string's length is between "min" and "max"
function isLengthBetween(str, min, max)
{
  return (str.length >= min)&&(str.length <= max);
}
// returns true if the string is a US phone number formatted as...
// (000)000-0000, (000) 000-0000, 000-000-0000, 000.000.0000, 000 000 0000, 0000000000
function isPhoneNumber(str)
{
  var re = /^\(?[2-9]\d{2}[\)\.-]?\s?\d{3}[\s\.-]?\d{4}$/
  return re.test(str);
}
// returns true if the string is a valid date formatted as...
// mm dd yyyy, mm/dd/yyyy, mm.dd.yyyy, mm-dd-yyyy
function isDate(str)
{
  var re = /^(\d{1,2})[\s\.\/-](\d{1,2})[\s\.\/-](\d{4})$/
  if (!re.test(str)) return false;
  var result = str.match(re);
  var m = parseInt(result[1]);
  var d = parseInt(result[2]);
  var y = parseInt(result[3]);
  
  if(m < 1 || m > 12 || y < 1900 || y > 2100) return false;
  
  if(m == 2){
          var days = ((y % 4) == 0) ? 29 : 28;
  }else if(m == 4 || m == 6 || m == 9 || m == 11){
          var days = 30;
  }else{
          var days = 31;
  }
  
  return (d >= 1 && d <= days);
}
// returns true if "str1" is the same as the "str2"
function isMatch(str1, str2)
{
  return str1 == str2;
}
// returns true if the string contains only whitespace
// cannot check a password type input for whitespace
function isWhitespace(str)
{ 												// NOT USED IN FORM VALIDATION
  var re = /[\S]/g
  if (re.test(str)) return false;
  return true;
}
// removes any whitespace from the string and returns the result
// the value of "replacement" will be used to replace the whitespace (optional)
function stripWhitespace(str, replacement)
{												// NOT USED IN FORM VALIDATION
  if (replacement == null) replacement = '';
  var result = str;
  var re = /\s/g
  if(str.search(re) != -1){
    result = str.replace(re, replacement);
  }
  return result;
}


function checkPhone()
{
	var stripped = strng.replace(/[\(\)\.\-\ ]/g, '');
	//strip out acceptable non-numeric characters
	if (isNaN(parseInt(stripped))) {
   		error = "The phone number contains illegal characters.";
	}
}
function isDifferent(strng) 
{
  var error = "";
  if (strng != "Can\'t touch this!") {
     error = "You altered the inviolate text area.\n";
  }
}
/*for (i=0, n=theForm.radios.length; i<n; i++) 
{
   if (theForm.radios[i].checked) {
      var checkvalue = theForm.radios[i].value;
      break;
   }
}
why += checkRadio(checkvalue);*/
 
function checkRadio(checkvalue) 
{
	var error = "";
    if (!(checkvalue)) {
       error = "Please check a radio button.\n";
    }
	return error;    
}
function checkDropdown(choice) 
{
    var error = "";
    if (choice == 0) {
       error = "You didn't choose an option from the drop-down list.\n";
    }    
	return error;
} 
<!--
/* This script and many more are available free online at
The JavaScript Source!! http://javascript.internet.com
Created by: David Leppek :: https://www.azcode.com/Mod10

Basically, the alorithum takes each digit, from right to left and muliplies each second
digit by two. If the multiple is two-digits long (i.e.: 6 * 2 = 12) the two digits of
the multiple are then added together for a new number (1 + 2 = 3). You then add up the 
string of numbers, both unaltered and new values and get a total sum. This sum is then
divided by 10 and the remainder should be zero if it is a valid credit card. Hense the
name Mod 10 or Modulus 10. */
function Mod10(ccNumb) 
{  							// v2.0
	var valid = "0123456789"  // Valid digits in a credit card number
	var len = ccNumb.length;  // The length of the submitted cc number
	var iCCN = parseInt(ccNumb);  // integer of ccNumb
	var sCCN = ccNumb.toString();  // string of ccNumb
	sCCN = sCCN.replace (/^\s+|\s+$/g,'');  // strip spaces
	var iTotal = 0;  // integer total set at zero
	var bNum = true;  // by default assume it is a number
	var bResult = false;  // by default assume it is NOT a valid cc
	var temp;  // temp variable for parsing string
	var calc;  // used for calculation of each digit
	
	// Determine if the ccNumb is in fact all numbers
	for (var j=0; j<len; j++) {
	  temp = "" + sCCN.substring(j, j+1);
	  if (valid.indexOf(temp) == "-1"){bNum = false;}
	}
	
	// if it is NOT a number, you can either alert to the fact, or just pass a failure
	if(!bNum){
	  /*alert("Not a Number");*/bResult = false;
	}
	
	// Determine if it is the proper length 
	if((len == 0)&&(bResult)){  // nothing, field is blank AND passed above # check
	  bResult = false;
	} else{  // ccNumb is a number and the proper length - let's see if it is a valid card number
	  if(len >= 15){  // 15 or 16 for Amex or V/MC
		for(var i=len;i>0;i--){  // LOOP throught the digits of the card
		  calc = parseInt(iCCN) % 10;  // right most digit
		  calc = parseInt(calc);  // assure it is an integer
		  iTotal += calc;  // running total of the card number as we loop - Do Nothing to first digit
		  i--;  // decrement the count - move to the next digit in the card
		  iCCN = iCCN / 10;                               // subtracts right most digit from ccNumb
		  calc = parseInt(iCCN) % 10 ;    // NEXT right most digit
		  calc = calc *2;                                 // multiply the digit by two
		  // Instead of some screwy method of converting 16 to a string and then parsing 1 and 6 and then adding them to make 7,
		  // I use a simple switch statement to change the value of calc2 to 7 if 16 is the multiple.
		  switch(calc){
			case 10: calc = 1; break;       //5*2=10 & 1+0 = 1
			case 12: calc = 3; break;       //6*2=12 & 1+2 = 3
			case 14: calc = 5; break;       //7*2=14 & 1+4 = 5
			case 16: calc = 7; break;       //8*2=16 & 1+6 = 7
			case 18: calc = 9; break;       //9*2=18 & 1+8 = 9
			default: calc = calc;           //4*2= 8 &   8 = 8  -same for all lower numbers
		  }                                               
		iCCN = iCCN / 10;  // subtracts right most digit from ccNum
		iTotal += calc;  // running total of the card number as we loop
	  }  // END OF LOOP
	  if ((iTotal%10)==0){  // check to see if the sum Mod 10 is zero
		bResult = true;  // This IS (or could be) a valid credit card number.
	  } else {
		bResult = false;  // This could NOT be a valid credit card number
		}
	  }
	}
	// change alert to on-page display or other indication as needed.
	if(bResult) {
	  alert("This IS a valid Credit Card Number!");
	}
	if(!bResult){
	  alert("This is NOT a valid Credit Card Number!");
	}
	  return bResult; // Return the results
}
// -->

function validatephone(xxxxx) 
{
	var maintainplus = '';
 	var numval = xxxxx.value
 	if ( numval.charAt(0)=='+' ){ var maintainplus = '+';}
 	curphonevar = numval.replace(/[\\A-Za-z!"£$%^&*+_={};:'@#~,.¦\/<>?|`¬\]\[]/g,'');
 	xxxxx.value = maintainplus + curphonevar;
 	var maintainplus = '';
 	xxxxx.focus;
}

function checkRadios() 
{
 var el = document.forms[0].elements;
 for(var i = 0 ; i < el.length ; ++i) {
  if(el[i].type == "radio") {
   var radiogroup = el[el[i].name]; // get the whole set of radio buttons.
   var itemchecked = false;
   for(var j = 0 ; j < radiogroup.length ; ++j) {
    if(radiogroup[j].checked) {
	 itemchecked = true;
	 break;
	}
   }
   if(!itemchecked) { 
    alert("Please choose an answer for "+el[i].name+".");
    if(el[i].focus)
     el[i].focus();
	return false;
   }
  }
 }
 return true;
}


function checkThisForm(formname, submitbutton, errors) 
{
  if (errors == '') {
    eval(formname+'.'+submitbutton+'.disabled=true');
    eval('document.'+formname+'.submit()');
  } else {
    alert(errors);
  }
}

function checkText(formname, textboxname, displaytext) 
{
  var localerror = '';
  if(Trim(eval('document.'+formname+'.'+textboxname+'.value'))=='') {
    localerror =  '- '+displaytext+' is Required.\n';
  } else localerror = '';
  return localerror;
}

function checkNum(formname, textboxname, displaytext) 
{
  var localerror = '';
  if(isNaN(eval('document.'+formname+'.'+textboxname+'.value'))) {
    localerror =  '- '+displaytext+' Should Be A Number With No Spaces.\n';
  } else localerror = '';
  return localerror;
}

function checkSpaces(formname, textboxname, displaytext) 
{
  var valid = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_'; // define valid characters
  var localerror = '';
  if(!isValid(Trim(eval('document.'+formname+'.'+textboxname+'.value')), valid)) {
    localerror =  '- '+displaytext+' Should Not Contain Spaces.\n';
  } else localerror = '';
  return localerror;
}

function checkSelect(formname, selectboxname, displaytext) 
{
  var localerror = '';
  if(eval('document.'+formname+'.'+selectboxname+'.selectedIndex')==0) {
    localerror =  '- '+displaytext+' is Required.\n';
  } else localerror = '';
  return localerror;
}

function getRadio(formname, radioname, displaytext) 
{
  for (var i=0; i < eval('document.'+formname+'.'+radioname+'.length'); i++) {
    if (eval('document.'+formname+'.'+radioname+'[i].checked')) {
      var rad_val = eval('document.'+formname+'.'+radioname+'[i].value');
      return rad_val;
    }
  }
}

function checkRadio(formname, radioname, displaytext) 
{
  var localerror = '';
  var rad_val    = '';
  for (var i=0; i < eval('document.'+formname+'.'+radioname+'.length'); i++) { //check every radio button by that name
    if (eval('document.'+formname+'.'+radioname+'[i].checked'))  { //if it is checked
      rad_val += '-';
      }	else rad_val += '';
      }
    if (rad_val=='') {
      localerror =  '- '+displaytext+' is Required.\n';
    }
  return localerror;
}

function autoComplete (field, select, property) 
{
/*onKeyUp="autoComplete(this,this.form.selectboxname,'value',false)" - add this to textbox where you are typing*/
  var found = false;
  for (var i = 0; i < select.options.length; i++) {
    if (select.options[i][property].toUpperCase().indexOf(field.value.toUpperCase()) == 0) {
      found=true; break;
    }
  }
  if (found) {
    select.selectedIndex = i;
  } else {
    select.selectedIndex = -1;
  }
  if (field.createTextRange) {
    if (!found) {
      field.value=field.value.substring(0,field.value.length-1);
      return;
    }
    var cursorKeys ="8;46;37;38;39;40;33;34;35;36;45;";
    if (cursorKeys.indexOf(event.keyCode+";") == -1) {
      var r1 = field.createTextRange();
      var oldValue = r1.text;
      var newValue = found ? select.options[i][property] : oldValue;
      if (newValue != field.value) {
        field.value = newValue;
        var rNew = field.createTextRange();
        rNew.moveStart('character', oldValue.length) ;
        rNew.select();
      }
    }
  }
}

function Trim(s) 
{
  while ((s.substring(0,1) == ' ') || (s.substring(0,1) == '\n') || (s.substring(0,1) == '\r')) {
    s = s.substring(1,s.length);
  }
  while ((s.substring(s.length-1,s.length) == ' ') || (s.substring(s.length-1,s.length) == '\n') || (s.substring(s.length-1,s.length) == '\r')) {
    s = s.substring(0,s.length-1);
  }
  return s;
}

function isValid(string,allowed) 
{
	//  var valid = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'; // define valid characters
    for (var i=0; i< string.length; i++) {
      if (allowed.indexOf(string.charAt(i)) == -1) return false;
    }
    return true;
}
function validate(field) 
{
	var valid = "abcdefghijklmnopqrstuvwxyz0123456789"
	var ok = "yes";
	var temp;
	for (var i=0; i<field.value.length; i++) {
	temp = "" + field.value.substring(i, i+1);
	if (valid.indexOf(temp) == "-1") ok = "no";
	}
	if (ok == "no") {
	alert("Invalid entry!  Only characters and numbers are accepted!");
	field.focus();
	field.select();
   }
}
function verifyIP (IPvalue) 
{
	errorString = "";
	theName = "IPaddress";
	
	var ipPattern = /^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/;
	var ipArray = IPvalue.match(ipPattern);
	
	if (IPvalue == "0.0.0.0")
	errorString = errorString + theName + ': '+IPvalue+' is a special IP address and cannot be used here.';
	else if (IPvalue == "255.255.255.255")
	errorString = errorString + theName + ': '+IPvalue+' is a special IP address and cannot be used here.';
	if (ipArray == null)
	errorString = errorString + theName + ': '+IPvalue+' is not a valid IP address.';
	else {
	for (i = 0; i < 4; i++) {
	thisSegment = ipArray[i];
	if (thisSegment > 255) {
	errorString = errorString + theName + ': '+IPvalue+' is not a valid IP address.';
	i = 4;
	}
	if ((i == 0) && (thisSegment > 255)) {
		errorString = errorString + theName + ': '+IPvalue+' is a special IP address and cannot be used here.';
		i = 4;
		  }
	   }
	}
	extensionLength = 3;
	if (errorString == "")
		alert ("That is a valid IP address.");
	else
		alert (errorString);
}


var ck_name = /^[A-Za-z0-9 ]{3,20}$/;
var ck_email = /^([\w-]+(?:\.[\w-]+)*)@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$/i 
var ck_username = /^[A-Za-z0-9_]{1,20}$/;
var ck_password =  /^[A-Za-z0-9!@#$%^&*()_]{6,20}$/;

function reportErrors(errors){
 var msg = "Please Enter Valide Data...\n";
 for (var i = 0; i<errors.length; i++) {
 var numError = i + 1;
  msg += "\n" + numError + ". " + errors[i];
}
 alert(msg);
}

function IsValidTime(timeStr) {
// Checks if time is in HH:MM:SS AM/PM format.
// The seconds and AM/PM are optional.

var timePat = /^(\d{1,2}):(\d{2})(:(\d{2}))?(\s?(AM|am|PM|pm))?$/;

var matchArray = timeStr.match(timePat);
if (matchArray == null) {
alert("Time is not in a valid format.");
return false;
}
hour = matchArray[1];
minute = matchArray[2];
second = matchArray[4];
ampm = matchArray[6];

if (second=="") { second = null; }
if (ampm=="") { ampm = null }

if (hour < 0  || hour > 23) {
alert("Hour must be between 1 and 12. (or 0 and 23 for military time)");
return false;
}
if (hour <= 12 && ampm == null) {
if (confirm("Please indicate which time format you are using.  OK = Standard Time, CANCEL = Military Time")) {
alert("You must specify AM or PM.");
return false;
   }
}
if  (hour > 12 && ampm != null) {
alert("You can't specify AM or PM for military time.");
return false;
}
if (minute<0 || minute > 59) {
alert ("Minute must be between 0 and 59.");
return false;
}
if (second != null && (second < 0 || second > 59)) {
alert ("Second must be between 0 and 59.");
return false;
}
return false;
}

function validatePwd() 
{
var invalid = " "; // Invalid character is a space
var minLength = 6; // Minimum length
var pw1 = document.myForm.password.value;
var pw2 = document.myForm.password2.value;
// check for a value in both fields.
if (pw1 == '' || pw2 == '') {
alert('Please enter your password twice.');
return false;
}
// check for minimum length
if (document.myForm.password.value.length < minLength) {
alert('Your password must be at least ' + minLength + ' characters long. Try again.');
return false;
}
// check for spaces
if (document.myForm.password.value.indexOf(invalid) > -1) {
alert("Sorry, spaces are not allowed.");
return false;
}
else {
if (pw1 != pw2) {
alert ("You did not enter the same new password twice. Please re-enter your password.");
return false;
}
else {
alert('Nice job.');
return true;
      }
   }
}

var menu_selection="";
var radio_selection="";
function  checkForm() 
{
	if (dropDownMenu() && radioButtons()) {
	document.forms[0].results1.value=menu_selection;
	document.forms[0].results2.value=radio_selection;
	alert("\nForm has been filled out correctly.");
   }
}
function dropDownMenu(form)  
{
	var myindex=document.forms[0].menu.selectedIndex;
	if (myindex==0) {
	alert("\nYou must make a selection from the drop-down menu.");
	document.forms[0].menu.focus();
	}
	else {
	menu_selection=document.forms[0].menu.options[myindex].value;
	return true;
   }
}
function radioButtons() 
{
	if (radio_selection=="")
	alert("\nYou must check one of the radio buttons.");
	else {
	return true;
   }
}
function resetForm() 
{
	document.forms[0].menu.options[0].selected = true;
	menu_selection="";
	radio_selection="";
}



function validaPhone(field) 
{
	var valid = "0123456789.()-+ "
	var ok = "no";
	var temp;
	for (var i=0; i<field.value.length; i++) 
	{	
		temp = "" + field.value.substring(i, i+1);
		//alert(valid.indexOf(temp));
		if (valid.indexOf(temp) == "-1") ok = "no";
		else ok = "yes";
	}
	if (ok == "no") 
	{
		//alert("Not a valid Phone Number!");
		return false;
   }
   else
   {
	   return true;
   }
}

function validate_date(date) 
{  
	if ( date.match(/^(\d{1,2})\-(\d{1,2})\-(\d{4})$/) ) 
	{  
		var dd = RegExp.$1;  
		var mm = RegExp.$2;  
		var yy = RegExp.$3;  
  
		// try to create the same date using Date Object  
		var dt = new Date(parseFloat(yy), parseFloat(mm)-1, parseFloat(dd), 0, 0, 0, 0);  
		
		// invalid day  
		if ( parseFloat(dd) != dt.getDate() ) { return false; }  
		// invalid month  
		if ( parseFloat(mm)-1 != dt.getMonth() ) { return false; }  
		// invalid year  
		if ( parseFloat(yy) != dt.getFullYear() ) { return false; }  
  
		// everything fine  
		return true;  
	} else 
	{  
		// not even a proper date  
		return false;  
	}  
} 

function validatedate(date) 
{  
	if ( date.match(/^[0-9]{4}\-(0[1-9]|1[012])\-(0[1-9]|[12][0-9]|3[01])/)) 
	{  
		// everything fine  
		return true;  
	} else 
	{  
		// not even a proper date  
		return false;  
	}  
} 

// Declaring valid date character, minimum year and maximum year
var dtCh= "/";
var minYear=1900;
var maxYear=2100;

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 isDateValid(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 || year<minYear || year>maxYear){
		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
}