Simple Javascript Form Validation

June 11, 2017 Email, HTML, Javascript, PHP, Tutorial

When it comes to contact forms, validating the information submitted by your visitors is key.

With proper form validation, we can help cut down fraudulent submissions and keep you relatively free from spam submissions as well. Below, I’ve gathered one of the simplest methods for validating your contact forms to keep your collected data valid and useful.

I’ve used javascript to validate my webform. You may copy and paste the code below to your site or application, but be sure to update the dependent code to match your web site.

One thing to remember is to invoke the javascript validation of your form with the ‘onSubmit’ tag.

I’ve Included 3 snippets of code to get your web form functioning and validating properly.  Although, the form is validated with javascript, I’ve used PHP to process the mailing function, so that your form sends on submit.

Part 1: The Contact Web Form

The form I’ve provided here is a very simple 4 field form to collect data for you web site or application. Here we’re gathering the basic information we need to gather from a visitor to contact them further regarding their inquiry. Here, we’re collecting Name, Email, Phone Number and their message or question.

<form class="form-container" name="myForm" method="post" onsubmit="return validateForm()" action="sendmail.php">
<div class="frm-element-lg fl">
<input type="text" name="name" id="name" class="icon-1" placeholder="Name*"></div>
<div class="frm-element-lg fl">
<input type="text" name="email" id="email" class="icon-3" placeholder="Email*"></div>
<div class="frm-element-lg fl">
<input type="text" name="phone" id="phone" class="icon-4" placeholder="Phone*" oninput="this.value = this.value.replace(/[^0-9.]/g, ''); this.value = this.value.replace(/(\..*)\./g, '$1');"></div>
<div class="frm-element-lg fl">
<input type="text" name="message" id="message" class="icon-5" placeholder="Message*"></div>
<div style="clear:both;"></div>
<input type="submit" value="Submit" class="submit-btn">

Part 2: The Form Validation

As stated above, we’re using javascript to validate our form submissions. Here, we set a javascript alert box to pop up on submission if a user has submitted incomplete form fields and we have set our email input field to confirm that the visitor is submitting a correctly formatted email address as well.

There are also 3rd party services you may integrate into your validation to confirm that the email provided is, in fact, a ‘real’ email as well, but that’s getting ahead of ourselves regarding our simple validation here.

<script type="text/javascript">
function validateForm() {
var x = document.forms["myForm"]["name"].value;
if (x == "") {
alert("Name must be filled out");
return false;
var x = document.forms["myForm"]["email"].value;
if (x == "") {
alert("Email Address must be filled out");
return false;
var x = document.forms["myForm"]["email"].value;
var atpos = x.indexOf("@");
var dotpos = x.lastIndexOf(".");
if (atpos<1 || dotpos<atpos+2 || dotpos+2>=x.length) {
alert("Not a valid e-mail address");
return false;
var x = document.forms["myForm"]["phone"].value;
if (x == "") {
alert("Phone number must be filled out");
return false;
var x = document.forms["myForm"]["message"].value;
if (x == "") {
alert("Message must be filled out");
return false;

Part 3: The Send Function

I’ve included the send function, as well, below. Here we use PHP to ‘send’ the email once the form is filled out by your site visitor and they click submit. You may take the code below and create a ‘sendmail.php’ file that is included in the form code above as the form action.

Be sure that all of your variables and form input name match correctly so that your send function operate correctly.

<?php $email_to = "";
$name = $_POST["name"];
$email_from = $_POST["email"];
$message = $_POST["message"];
$phone = $_POST["phone"];

$email_subject = "Feedback from website"; $headers = "From: " . $email_from . "\n";
$headers .= "Reply-To: " . $email_from . "\n"; $message = "Name: ". $name . "\r\nEmail: " . $email_from . "\r\nMessage: " . $message . "\r\nPhone: " . $phone;
ini_set("sendmail_from", $email_from);
$sent = mail($email_to, $email_subject, $message, $headers, "-f" .$email_from);
if ($sent) { header("Location:"); }
else { echo "There has been an error sending your comments. Please try later."; }

There’s several ways available to validate and send your web forms. The method above, I’ve found, is the lightest and simplest way to achieve web form validation. I hope this helps and enjoy.