Dynamic PageNumbers for Flipbook using turn.js

So, I was given a task of creating a Custom Flipbook, where using images in div tags, I was successful in creating one. Users could turn pages using prev/next buttons or flipping through them by the corners like shown for other Flipbooks.

My concern is Displaying PageNumbers. Changing pages through the buttons, pages change dynamically but when flipping through turn.js the page number does not update.

I am providing the snippet of the code that I have used. Any kind of help and guidance is appreciated !!

<!DOCTYPE html>

<head>
  <title>Flipbook Demo</title>
  <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.0/jquery.min.js"></script>
  <script type="text/javascript" src="turn.min.js"></script>
</head>
<style>
  body{
    background-color: #313131;
  }

  #flipbook {
    margin-top: 1.5%;
    margin-left: 6%;
    width: 1130px;
    height: 800px;
    position: relative;
    overflow: hidden;
  }

  #nav_controls{
      margin: 1.5%;
      margin-left: 44%;
  }
  
</style>
    <body> 
        <h1 style="color: white; margin-left: 43%">FITI5 WHITEPAPER</h1>
        <div id="flipbook">
            <!-- Include Pages into div that you want to include -->
        </div>
        
        <div id="nav_controls">
            <button id="startdoc"><-</button>
            <button id="prev_page"> PREV </button>
            <span id="pgnos" style="margin-left: 2%; color: white;">1</span>   
            <button id="next_page" style="margin-left: 2%;"> NEXT </button>
            <button id="enddoc">-></button>
            <!--
            <button id="zoom-in">+</button>
            <buton id="zoom-out">-</button>-->
        </div>

        <script type="text/javascript">
            const startButton = document.querySelector("#startdoc");
            const endButton = document.querySelector("#enddoc");
            const prevButton = document.querySelector("#prev_page");
            const nextButton = document.querySelector("#next_page");
            const showPG = document.querySelector("#pgnos");
            
            //magnify = document.querySelector("#zoom-in");
            //minify = document.querySelector("#zoom-out");

            /*
            magnify.addEventListener('click', function() {
                $("#flipbook").turn("zoom", 1.1, 1);
            });
            minify.addEventListener('click', function() {
                $("#flipbook").turn("zoom", 1, 1.1);
            })  
            */
            
            $("#flipbook").turn({
                gradients: true,
                page: 1,
                duration: 2000
            });


            const first_page = $("#flipbook").turn("page");
            const last_page = $("#flipbook").turn("pages");    
            
            
            startButton.addEventListener('click', function() {
                $("#flipbook").turn("page", first_page);
                showPG.innerHTML = first_page;
            });

            endButton.addEventListener('click', function() {
                $('#flipbook').turn("page", last_page);
                showPG.innerHTML = last_page;
            });

            nextButton.addEventListener('click', function() {
                $("#flipbook").turn("next");
                showPG.innerHTML = $("#flipbook").turn("page");
            });

            prevButton.addEventListener('click', function() {
                $("#flipbook").turn("previous");
                showPG.innerHTML = $("#flipbook").turn("page");             
            });


            if ( (($("#flipbook").turn("page") == first_page)) ) {
                $(nextButton).click(function() {
                    $("#flipbook").animate({left: "275"});
                });

                $(endButton).click(function() {
                    $("#flipbook").animate({left: "565"});
                });

                $(prevButton).click(function() {
                    $("#flipbook").animate({left: "275"});
                });

                $(startButton).click(function() {
                    $("#flipbook").animate({left: "0"});
                });
            } 


            if ( (($("#flipbook").turn("page") == last_page)) ) {
                $(prevButton).click(function() {
                    $("#flipbook").animate({left: "300"});
                });   
            }

      
        </script>
    </body>
</html>