Javascript Validation with Regular Expression

Form validation

checkWholeForm()
------------------------------------------

function checkWholeForm(theForm) {
    var why = "";
    why += checkEmail(theForm.email.value);
    why += checkPhone(theForm.phone.value);
    why += checkPassword(theForm.password.value);
    why += checkUsername(theForm.username.value);
    why += isEmpty(theForm.notempty.value);
    why += isDifferent(theForm.different.value);
    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);
    why += checkDropdown(theForm.choose.selectedIndex);
    if (why != "") {
       alert(why);
       return false;
    }
return true;
}
-----------------------------------------------

checkUsername()
----------------------------------------------------------------------

function checkUsername (strng) {
 var error = "";
 if (strng == "") {
    error = "You didn't enter a username.\n";
 }
---------------
if ((strng.length < 4) || (strng.length > 10)) {
    error = "The username is the wrong length.\n";

}
----------------
var illegalChars = /\W/;
  // allow only letters, numbers, and underscores
    if (illegalChars.test(strng)) {
       error = "The username contains illegal characters.\n";
    } 
--------------------------------------------------------------------

checkPassword()

function checkPassword (strng) {
 var error = "";
 if (strng == "") {
    error = "You didn't enter a password.\n";
 }
    var illegalChars = /[\W_]/; // allow only letters and numbers
    if ((strng.length < 6) || (strng.length > 8)) {
       error = "The password is the wrong length.\n";
    }
    else if (illegalChars.test(strng)) {
      error = "The password contains illegal characters.\n";
    }
--------------------------------------------------------------
else if (!((strng.search(/[a-z]+/) > -1)
  && (strng.search(/[A-Z]+/) > -1)
  && (strng.search(/[0-9]+/) > -1))) {
  error = "The password must contain at least one 
    uppercase letter, one lowercase letter,
    and one numeral.\n";
  }
----------------------------------------------------------

checkEmail()

var emailFilter=/^.+@.+\..{2,3,4,6}$/;
if (!(emailFilter.test(strng))) { 
       error = "Please enter a valid email address.\n";
}
---------------
var illegalChars= /[\(\)\<\>\,\;\:\\\/\"\[\]]/
if (strng.match(illegalChars)) {
   error = "The email address contains illegal characters.\n";

}
------------------------------------------------------------------

checkPhone()

var stripped = strng.replace(/[\(\)\.\-\ ]/g, '');
//strip out acceptable non-numeric characters
if (isNaN(parseInt(stripped))) {
   error = "The phone number contains illegal characters.";
}
------------
if (!(stripped.length == 10)) {
 error = "The phone number is the wrong length.
   Make sure you included an area code.\n";
}
--------------------------------------------------------

checkRadio()

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;    
}
-------------------------------------------------------

check Dropdown()

function checkDropdown(choice) {
    var error = "";
    if (choice == 0) {
       error = "You didn't choose an option
         from the drop-down list.\n";
    }    
return error;
}    
-------------------------------------------------------
Numeric /Numbers only validation

 function numeric_validate(val)
 {     
     var rege = /^\d+$/;     
     if(rege.test(val))     
         return true     
     else         
         return false
     
 }