How to check form validation in jQuery code example

Example 1: form validation using jquery

<script src="https://cdn.jsdelivr.net/jquery.validation/1.16.0/jquery.validate.min.js"></script>
then add javascript code:
$(document).ready(function() {
   $("#form").validate();
});
</script>

Example 2: form validation using jquery

jQuery(document).ready(function() {
   jQuery("#forms).validate({
      rules: {
         firstname: 'required',
         lastname: 'required',
         u_email: {
            required: true,
            email: true,//add an email rule that will ensure the value entered is valid email id.
            maxlength: 255,
         },
      }
   });
});

Example 3: jquery form validation

function submitFunction(event){
	event.preventDefault();
}
$("#form_id").submit(submitFunction);