html input validation error message code example

Example 1: html form validation

<form action="">
    <label for="name">Username</label>
    <input id="name" type="text" required />
    <label for="Email">Email</label>
    <!-- The required attribute will prompt the user to make sure  -->
    <!-- the fields are not empty, and that the email is formatted correctly -->
    <!-- if you want to use custom validation you should use regex in JavaScript -->
    <input id="Email" type="text" required />
</form>

Example 2: input show validation message

// Validate emai

var applicationForm = document.getElementById("applicationForm");    
if (applicationForm.checkValidity()) {
  applicationForm.submit();
} else {
  applicationForm.reportValidity();
}