<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <button class='up'>销量升序</button>
    <button class='down'>销量降序</button>
    <ul></ul>

    <script>
        var cups = [
            { type: 1, price: 100, color: 'black', sales: 3000, name: '牛客logo马克杯' },
            { type: 2, price: 40, color: 'blue', sales: 1000, name: '无盖星空杯' },
            { type: 4, price: 60, color: 'green', sales: 200, name: '老式茶杯' },
            { type: 3, price: 50, color: 'green', sales: 600, name: '欧式印花杯' }
        ]
        var ul = document.querySelector('ul');
        var upbtn = document.querySelector('.up');
        var downbtn = document.querySelector('.down');

        // 补全代码
        upbtn.onclick = () => {
            //清空li
            ul.innerHTML = '';
            cups.sort((a, b) => a.sales - b.sales);
            // console.log(cups);
            let res = document.createDocumentFragment();
            for (let item of cups) {
                let li = document.createElement('li');
                li.innerHTML = item.name;
                res.appendChild(li);
            }
            ul.appendChild(res);

        }
        downbtn.onclick = () => {
            //清空li
            ul.innerHTML = '';
            cups.sort((a, b) => b.sales - a.sales);
            // console.log(cups);
            let res = document.createDocumentFragment();
            for (let item of cups) {
                let li = document.createElement('li');
                li.innerHTML = item.name;
                res.appendChild(li);
            }
            ul.appendChild(res);

        }

    </script>
</body>

</html>