<script type="text/javascript">
function validateForm (submit) { 

var errmsg = "Oops, you're required to complete the following fields! \n";
if (submit.email.value.search(/^\w+((-\w+)|(\.\w+))*\@[A-Za-z0-9]+((\.|-)[A-Za-z0-9]+)*\.[A-Za-z0-9]+$/) == -1) {
errmsg = errmsg + " - Valid email\n";
}

//Validate other form fields, etc, etc.
if (submit.name.value=="") {
errmsg = errmsg + " - Full Name\n";
}

//alert if fields are empty and cancel form submit
if (errmsg == "Oops, you're required to complete the following fields! \n") {
sub.submit();
}
else {
alert(errmsg);
return false;
}

<script type="text/javascript">
function validateForm (submit) { 

var errmsg = "Oops, you're required to complete the following fields! \n";
if (submit.email.value.search(/^\w+((-\w+)|(\.\w+))*\@[A-Za-z0-9]+((\.|-)[A-Za-z0-9]+)*\.[A-Za-z0-9]+$/) == -1) {
errmsg = errmsg + " - Valide email\n";
}

//Validate other form fields, etc, etc.
if (submit.name.value=="") {
errmsg = errmsg + " - Full Name\n";
}

//alert if fields are empty and cancel form submit
if (errmsg == "Oops, you're required to complete the following fields! \n") {
sub.submit();
}
else {
alert(errmsg);
return false;
}

<form>
<input>

Javascript email validation

email, javascript, validation

JavaScript