AjaxCode.js

<script>
  $(function(){

    let allComments =  document.getElementById("all-comments");
    let $name = $("#name");
    let $comment = $("#comment");

    $("#submit").on('click', function(){
        
        //validation to prevent html tags being inputted input box
        var reg =/<(.|\n)*?>/g;

        if (reg.test($('#comment').val()) == true) {
            var errorText ='HTML Tags Not Allowed';
            alert(errorText);
        }
        else  
        {
            var item =
            {
                username: $name.val(),
                comment: $comment.val(),
                postId: window.location.pathname,
            };

            $.ajax({
                type: "POST",
                url: "[your-api-url-here]]",
                data: JSON.stringify(item),
                contentType: "application/json",
                success : function(){
                    alert("Comment submitted successfully")
                    location.reload();
            },
            error : function(err){
                alert("error in post" + JSON.stringify(err))
            }
            });
        }

        $name.val("");
        $comment.val("");
    });
  });
</script>