validate email input javascript onchange
<script type="text/javascript">
function ShowAlert() {
var email = document.getElementById('txtEmailId');
var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
if (!filter.test(email.value)) {
alert('Please provide a valid email address');
email.focus;
return false;
}
else {
alert("Thanks for your intrest in us, Now you
will be able to receive monthly updates from us.");
document.getElementById('txtEmailId').value = "";
}
}
</script>