Contact form add * to required fields

<script>
( function( $ ) {
    $( document ).ready( function() {
        var requiredInput = $( '.et_pb_contact_field input[data-required_mark="required"]' );
        requiredInput.each(function(){
           var placeholder = $(this).attr('placeholder');
           $(this).attr("placeholder", placeholder+"*");
        })
    } );
} )( jQuery );
</script>