validate email javascript using html5 input validation code example

Example 1: validate email javascript

function validateEmail(email) {
    const re = /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
    return re.test(String(email).toLowerCase());
}

Example 2: 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>