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Javascript form validation only working once

Script: NewsletterScript.js
function formValidation() {
var fname = document.getElementById('firstName').value;
var lname = document.getElementById('lastName').value;
var pnumber = document.getElementById('phoneNumber').value;
var email = document.getElementById('e-mail').value;
if (FirstName(fname)) {
}
if (LastName(lname)) {
}
if (Country(country)) {
}
if (Email(email)) {
}
return false;
}
/*first name input validation*/
function FirstName(fname) {
var message = document.getElementsByClassName("error-message");
var letters = /^[A-Za-z]+$/;
if ( fname =="" || fname.match(letters)) {
text="";
message[0].innerHTML = text;
return true;
}
else {
text="First name should contain only letters";
message[0].innerHTML = text;
return false;
}
}
/*last name input validation*/
function LastName(lname) {
var message = document.getElementsByClassName("error-message");
var letters = /^[A-Za-z]+$/;
if ( lname =="" || lname.match(letters)) {
text="";
message[1].innerHTML = text;
return true;
}
else {
text="Last name should contain only letters";
message[1].innerHTML = text;
return false;
}
}
I'm trying to get this validation to loop until the criteria is fulfilled, currently this is only working once and if the button is clicked again it submits regardless. Button below.
Due to the script being so long its not letting me upload all of it, however its just got other validation such as phone number etc, Any help will be appreciated, cheers!

If what you want is that formValidation() returns true only when the four validation functions return true you sould write that instead of putting empty if statements :
return FirstName(fname) && LastName(lname) && Country(country) && Email(email);
This manner formValidation() will return false if one of them return false

You should consider using form onsubmit instead on the onclick on the submit button.
Instead of:
<input class="button" type="submit" value="Submit" name="submit" onClick="formValidation()" />
consider using the form submit and do not forget the return keyword:
<form onsubmit="return formValidation();" > /* ... */ </form>
Related Question: HTML form action and onsubmit issues

Javascript show validation message right after the text box

I am trying to validate a form using javascript. On button click function I have called a javascript function where I have displayed the message after the text box. The number of times I click the button same number of times message gets displayed just below the existing validation message. Please help me
Here goes my code:
function check() {
var v = true;
if ((document.getElementById('firstname').value == "")) {
$('#firstname').after('Validation message');
document.getElementById('firstname').style.borderColor='#DA394B';
v = false;
}
if ((document.getElementById('lastname').value == "")) {
$('#lastname').after('Some validation text');
document.getElementById('lastname').style.borderColor = '#DA394B';
v = false;
}
return v;
}

Assuming I understand what v is for. Which i probably don't because v (I hate one letter variable names...).
Try this:
function check() {
var v = true;
if ((document.getElementById('firstname').value == "")) {
if ($('#firstnameMessage').length <= 0)
{
$('#firstname').after('<p id="firstnameMessage">Validation message</p>');
document.getElementById('firstname').style.borderColor='#DA394B';
}
v = false;
}
if ((document.getElementById('lastname').value == "")) {
if ($('#lastnameMessage').length <= 0)
{
$('#lastname').after('<p id="lastnameMessage">Some validation text</p>');
document.getElementById('lastname').style.borderColor = '#DA394B';
}
v = false;
}
return v;
}
Simple fiddle to show this working: https://jsfiddle.net/srLt7wo0/

Using .after will insert another element per http://api.jquery.com/after/
The below solution uses a separate element already in the HTML to display the error message. If you use .after you have to check that you have not already added an element to your HTML
HTML
<input id="firstname" type="text"/><div id="firstnameMessage"></div>
<input id="lastname" type="text"/><div id="lastnameMessage"></div>
JS
function check() {
$("#firstnameMessage,#lastnameMessage").text(''); // clear message, reset border color
document.getElementById('firstname').style.borderColor='';
document.getElementById('lastname').style.borderColor='';
var isValid = true;
if ((document.getElementById('firstname').value == "")) {
$('#firstnameMessage').text('First name is required');
document.getElementById('firstname').style.borderColor='#DA394B';
isValid = false;
}
if ((document.getElementById('lastname').value == "")) {
$('#lastnameMessage').text('Last name is required');
document.getElementById('lastname').style.borderColor='#DA394B';
isValid = false;
}
return isValid;
}

I'm not sure to have understood you issue but maybe this could help you :)
window.firstname = document.getElementById('firstname')
window.lastname = document.getElementById('lastname')
window.issue = document.getElementById('issue')
function check() {
if(firstname.value == '' || lastname.value == '') {
issue.innerHTML = 'Please, use correct credentials.'
} else {
issue.innerHTML = ''
}
}
<input id="firstname" />
<input id="lastname" />
<button onclick="check()">
Check
</button>
<div id="issue" style="color:red;"></div>

This should work if i understand you.
It will add only one message no matter how many times you click
function check() {
var v = true;
if ((document.getElementById('firstname').value == "")) {
$('#message').remove()
$('#firstname').after('<span id='message'>Validation message</span>');
document.getElementById('firstname').style.borderColor='#DA394B';
v = false;
}
if ((document.getElementById('lastname').value == "")) {
$('#message').remove()
$('#lastname').after('<span id='message'>Some validation text</span>');
document.getElementById('lastname').style.borderColor = '#DA394B';
v = false;
}
return v;
}

Check the length of the number entered in a textbox

I want to write in text box and check if is integer and less than 16 numbers. I have the following JavaScript codes.
<script type="text/javascript">
function doCheck(field) {
if (isNaN(document.getElementById(field).value)) {
alert('this is not a number');
document.getElementById(field).focus();
document.getElementById(field).select();
return false;
}
else {
return true;
}
}
</script>
<form method="post" action="" onsubmit="return doCheck('number');">
national id=<input type="text" name="nat" id="number">
<input type="submit" name="submit">
</form>

document.getElementById(field).value.length

you can find the length of string inside the text box using this
function doCheck(field) {
var len = document.getElementById("number").val().length;
if(parse.Int(document.getElementById(field).value) && len < 16) {
return true;
}
else {
alert('your alert');
document.getElementById(field).focus();
document.getElementById(field).select();
return false;
}
}

be sure you parse it as an integer.
function doCheck(field) {
var input_value = document.getElementById(field).value;
if(isNaN(input_value) || parseInt(input_value,10) != input_value || input_value.length < 16) {
alert('this is not a number');
document.getElementById(field).focus();
document.getElementById(field).select();
return false;
}
else{
return true;
}
}

isNAN() checks whether a number is an illegal number of any type, not only integer. So you have to use something else there, a regular expressions maybe.
To get the length of the field you can simply use:
document.getElementById(field).value.length

Form validation doesn't like me

Second edit: OH MY GODS I'M AN IDIOT!!! I was focusing on the javascript and completely neglected the lack of a "result" item in the html...Thanks to those who helped!
Edit: Thanks so far. I corrected the errors that people pointed out but it still doesn't like me. :( My html is below.
I'm following a tutorial on html.net (lesson 16 on Javascript) and I've written it exactly how it's supposed to be written. I even loaded up the javascript file of the working tutorial page and compared (was the same)...then copied it and pasted it into my file just to be sure and it still doesn't work. If anyone could offer an opinion, that'd be wonderful. Code is below:
<html>
<head>
<title>Lesson 16: form validation</title>
<script type="text/javascript" src="lesson16.js"></script>
</head>
<body>
<h1>Lesson 16: Form validation</h1>
<form id="myForm" action="#" method="post">
<fieldset>
<p><label for="txtName">Name: </label>
<input type="text" id="txtName" name="txtName" />
</p>
<p><label for="txtEmail">Email: </label>
<input type="text" id="txtEmail" name="txtEmail" />
</p>
<p><input type="submit" value="Submit" /></p>
</fieldset>
</form>
</body>
</html>
function init()
{
var myForm = document.getElementById("myForm");
myForm.onsubmit = validate;
}
onload = init;
function validate()
{
var name = document.getElementById("txtName").value;
var email = document.getElementById("txtEmail").value;
var isRequiredNameSet = false;
var isRequiredEmailSet = false;
var isEmailValid = false;
var message = "";
isRequiredNameSet = validateRequired(name);
isRequiredEmailSet = validateRequired(email);
isEmailValid = validateEmail(email);
if (isRequiredNameSet && isRequiredEmailSet && isEmailValid)
{
message = "Thank you, you know how to follow instructions...good for you.";
}
else if (! isRequiredNameSet)
{
message = "Please, enter a name. First thing and you got it wrong...";
writeMessage(message);
return false;
}
else if (! isRequiredEmailSet)
{
message = "Please, enter an email...come on, it's not that hard...";
writeMessage(message);
return false;
}
else if (! isEmailValid)
{
message = "A valid email, numb nuts...with an # symbol and a .com or whatever...GODS!!";
writeMessage(message);
return false;
}
alert(message);
}
function validateRequired(input)
{
var isValid = false;
if (input.length == 0)
{
isValid = false;
}
else
{
isValid = true;
}
return isValid;
}
function validateEmail(email)
{
var isValid = false;
if (email.indexOf("#") == -1 || email.indexOf(".") == -1)
{
isValid = false;
}
else
{
isValid = true;
}
return isValid;
}
function writeMessage(text)
{
var paragraph = document.getElementById("result");
if (paragraph.firstChild)
{
paragraph.removeChild(paragraph.firstChild);
}
paragraph.appendChild(document.createTextNode(text));
}

you have IsRequiredNameSet in the else if (in validate function), but it should be isRequiredNameSet.
NOTE: you can chage your validateRequired() ... to function validateRequired(input) { return !!input.length; }

The problem is the line myForm.onsubmit = validate();... where you are invoking the validate function instead os assigning it as a reference to onsubmit
myForm.onsubmit = validate;
The same applies to onload also
onload = init;
Then you have a problem in case of isRequiredEmailSet
function validate() {
var name = document.getElementById("txtName").value;
var email = document.getElementById("txtEmail").value;
var isRequiredNameSet = false;
var isRequiredEmailSet = false;
var isEmailValid = false;
var message = "";
isRequiredNameSet = validateRequired(name);
isRequiredEmailSet = validateRequired(email);
isEmailValid = validateEmail(email);
if (isRequiredNameSet && isRequiredEmailSet && isEmailValid) {
message = "Thank you, you know how to follow instructions...good for you.";
} else if (!isRequiredNameSet) {
message = "Please, enter a name. First thing and you got it wrong...";
writeMessage(message);
return false;
} else if (!isRequiredEmailSet) {
message = "Please, enter an email...come on, it's not that hard...";
writeMessage(message);
return false;
} else if (!isEmailValid) {
message = "A valid email, numb nuts...with an # symbol and a .com or whatever...GODS!!";
writeMessage(message);
return false;
}
alert(message);
}
Demo: Fiddle

javascript validation numerical

Hi sorry i'm still pretty new to javascript.
I've developed a form in HTML and now i'm attempting to add javascript to validate the form.
So far i have simple javascript to make sure each element is filled in,
if (document.order.suburb.value=="")
{
alert("Suburb Cannot Be Empty")
return false
}
if (document.order.postcode.value=="")
{
alert("Postcode Cannot Be Empty")
return false
}
I then have javascript to validate the length of some of the elements,
if (document.order.telephone.value.length < 10)
{
alert("Invalid Telephone Number")
return false
}
Now i'm trying to validate numeric values in the telephone number part but it's not executing correctly, it's like the code is just ignored when it's being executed.
var digits="0123456789"
var temp
var i
for (i = 0 ; i <document.order.telephone.value.length; i++)
{
temp=document.order.telephone.value.substring(i,i+1)
if (digits.indexOf(temp)==-1)
{
alert("Invalid Telephone Number")
return false
}
}
Thanks for reading and thanks for the help :) been stuck on this issue for weeks and have no idea what i'm doing wrong, i tried to code on a separate document with another form and it seemed to work fine.
EDIT
Code for validation for digits in postcode
var post = document.order.postcode.value.replace(white,'');
if(!post){
alert("Post code required !");
return false;
}
post = post.replace(/[^0-9]/g,'');//replace all other than digits
if(!post || 4 > postcode.length) {
alert("Invalid Postcode !");
return false;
}

You may try this example:
var validate = function() {
var white = /\s+/g;//for handling white spaces
var nonDigit = /[^0-9]/g; //for non digits
if(!document.order.suburb.value.replace(white, '')) {
alert("Suburb required !");
return false; //don't allow to submit
}
var post = document.order.postcode.value.replace(white, '')
if(!post) {
alert("Post code required !");
return false;
}
post = post.replace(nonDigit,'');//replace all other than digits
if(!post || 6 > post.length) { //min post code length
alert("Invalid Post code !");
return false;
}
var tel = document.order.telephone.value.replace(white, '');
if(!tel) {
alert("Telephone required !");
return false;
}
tel = tel.replace(nonDigit,'');
if(!tel || 10 > tel.length) {
alert("Invalid Telephone !");
return false;
}
return true; //return true, when above validations have passed
};
<form onsubmit="return validate();" action="#" name="order">
Suburb: <input type="text" id="suburb" name="suburb" ><br/>
Post code: <input type="text" id="postcode" name="postcode"/><br/>
Telephone: <input type="text" id="telephone" name="telephone"/><br/>
<input type="reset"/><input type="submit"/>
</form>

Here is a FIDDLE that will give you something to think about.
You could handle this task in hundreds of ways. I've just used a regex and replaced all of the non-numbers with '' - and compared the length of two variables - if there is anything other than a number the length of the regex variable will be shorter than the unchanged mytelephone.
You can do all kinds of "validation" - just me very specific in how you define "valid".
JS
var mysuburb, mypostcode, mytelephone;
$('.clickme').on('click', function(){
mysuburb = $('.suburb').val();
mypostcode = $('.postcode').val();
mytelephone = $('.telephone').val();
console.log(mysuburb + '--' + mypostcode + '--' + mytelephone);
if(mysuburb.length < 1)
{
$('.errorcode').html('');
$('.errorcode').append('Suburb is required');
return false;
}
if(mypostcode.length < 1)
{
$('.errorcode').html('');
$('.errorcode').append('postode is required');
return false;
}
if( mytelephone.length < 1 )
{
$('.errorcode').html('');
$('.errorcode').append('telephone number is required');
return false;
}
if( mytelephone.length != mytelephone.replace(/[^0-9]/g, '').length)
{
$('.errorcode').html('');
$('.errorcode').append('telephone number must contain only numbers');
return false;
}
});