Pagination in React, Node.js and MongoDB

<script src="js/babel.min.js"></script>
<script src="js/react.development.js"></script>
<script src="js/react-dom.development.js"></script> 

<div id="app"></div>

<script type="text/babel">

    function App() {

        // Set current page
        const [page, setPage] = React.useState(1);

        // Number of pages on pagination
        const [pages, setPages] = React.useState(0);

        // Whenever it's value is updated, the data will be re-fetched
        const [refetch, setRefetch] = React.useState(0);

        // Data array
        const [users, setUsers] = React.useState([]);

        // Check if there are more pages
        const [hasMorePages, setHasMorePages] = React.useState(false);

        async function loadMore() {
            // Creating a built-in AJAX object
            var ajax = new XMLHttpRequest();

            // Tell the method, URL of request and make is asynchronous
            ajax.open("POST", "http://localhost:3000/fetch-users", true);

            // Detecting request state change
            ajax.onreadystatechange = function () {

                // Called when the response is successfully received
                if (this.readyState == 4) {

                    if (this.status == 200) {
                        // For debugging purpose only
                        // console.log(this.responseText);

                        // Converting JSON string to Javasript array
                        var response = JSON.parse(this.responseText);

                        // Update state variable
                        setUsers(response.users);

                        // Set if there are more pages
                        setHasMorePages(response.hasMorePages);

                        // Set pagination
                        setPages(response.pages);
                    }
                }
            };

            // Create form data object
            const formData = new FormData();

            // Attach current page number
            formData.append("page", page);

            // Send the request
            ajax.send(formData);
        }

        // Run function when page value updates
        React.useEffect(function () {
            loadMore();
        }, [refetch]);

        return (
            <>
                {/* Display data */}

                { users.map(function (user) {
                    return (
                        <p key={ `user-${ user._id }` }>{ user.name }</p>
                    );
                }) }

                {/* Show pagination if required */}
                
                { pages > 1 && (
                    <nav>
                        <ul>
                            { Array.from({ length: pages }, function (_, index) { return index + 1 } ).map(function (p) {
                                return (
                                    <li key={ `pagination-${ p }` } className={ `page-item ${ p == page ? "active" : "" }` }>
                                        <a href="#" onClick={ function (event) {
                                            event.preventDefault();
                                            setPage(p);
                                            setRefetch(refetch + 1);
                                        } }>{ p }</a>
                                    </li>
                                );
                            }) }
                        </ul>
                    </nav>
                ) }
            </>
        );

    }

    ReactDOM.createRoot(
        document.getElementById("app")
    ).render(<App />);

</script>

const express = require("express");
const app = express();
const http = require("http").createServer(app);

const mongodb = require("mongodb");
const ObjectId = mongodb.ObjectId;
const MongoClient = mongodb.MongoClient;

const cors = require("cors");
app.use(cors("http://localhost/pagination-in-react-node-js-and-mongodb"));

const expressFormidable = require("express-formidable");
app.use(expressFormidable({
    multiples: true
}));

const port = process.env.PORT || 3000;
const databaseName = "test"
const MONGO_URI = process.env.MONGO_URI || "mongodb://127.0.0.1:27017";

http.listen(port, async function () {
    console.log("Server started");

    const client = new MongoClient(MONGO_URI);
    try {
        await client.connect();
        const db = client.db(databaseName);
        console.log("Database connected.");

        app.post("/fetch-users", async function (request, result) {
            const limit = 2;
            const page = parseInt(request.fields.page || 1);
            const skip = (page - 1) * limit;

            const users = await db.collection("users")
                .find({})
                .sort({
                    _id: 1
                })
                .skip(skip)
                .limit(limit)
                .toArray();

            const usersArr = [];
            for (let a = 0; a < users.length; a++) {
                const obj = {
                    _id: users[a]._id || "",
                    name: users[a].name || ""
                };

                usersArr.push(obj);
            }

            const totalCount = await db.collection("users").countDocuments({});
            const hasMorePages = (page * limit) < totalCount;
			const pages = Math.ceil(totalCount / limit);

            result.json({
                status: "success",
                message: "Data has been fetched.",
                users: users,
                hasMorePages: hasMorePages,
                pages: pages
            });
        });

    } catch (exp) {
        console.log(exp.message);
    }
});