JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-2.2.3.min.js"></script>
 <table border='1'>
            <tr>
                <th>Product</th>
                <th>Price</th>
                <th>Quantity</th>
            </tr>
            <tr>
                <td>APPLE</td>
                <td>35</td>
                <td>
                    <input type='text' />
                    <button>加到購物車</button>
            </tr>
            <tr>
                <td>BANANA</td>
                <td>18</td>

                <td>
                    <input type='text' />
                    <button>加到購物車</button>
            </tr>
            <tr>
                <td>TOMATO</td>
                <td>39</td>

                <td>
                    <input type='text' />
                    <button>加到購物車</button>

            </tr>
            <tr>
                <td>ORANGE</td>
                <td>17</td>

                <td>
                    <input type='text' />
                    <button>加到購物車</button>
            </tr>
            <tr>
                <td>LEMON</td>
                <td>28</td>
                <td>
                    <input type='text' />
                    <button>加到購物車</button>
            </tr>
            <tr>
                <td>TOTAL</td>
                <td></td>
                <td colspan="2" id='total'></td>
            </tr>

        </table>

JavaScript

$(document).ready(function () {
            let totalNum = localStorage.getItem('xyz'); //從localstorage取得加總金額
            localStorage.getItem('abx'); //從localstorage取得單價乘以數量
            $('button').click(function () {
                let qunt = $(this).prev().val(); //取得input的金額
                localStorage.setItem('abc', qunt); //將價格記錄在localstorage
                let pri = $(this).closest('td').prev('td').html(); //取得原本設定的單價
                //let totalNum = 0; //加總初始值是0
                let total = qunt * pri; //單價乘以數量
                totalNum = (totalNum ? parseInt(totalNum) : 0) + parseInt(total); //把之前按的加總
                $('#total').text(totalNum); //把加總的印在總額裡面
                localStorage.setItem('xyz', $('#total').val()); //紀錄加總金額在localstorage
            })
        })