<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 = () => {
            let upCups = cups.slice().sort((a, b) => {
                return a.sales - b.sales
            })
            ul.innerHTML = upCups.map(c => '<li>' + c.name + '</li>').join()
        }
        downbtn.onclick = () => {
            let downCups = cups.slice().sort((a, b) => {
                return b.sales - a.sales
            })
            ul.innerHTML = downCups.map(c => '<li>' + c.name + '</li>').join()
        }
    </script>