SOURCE

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
let renderList = arr => {
    var str = '';
    arr.forEach(element => {
        str += `<li>${element.name}</li>`
    })
    ul.innerHTML = str
}

upbtn.onclick = function () {
    var upArr = cups.sort((a, b) => { return a.sales - b.sales })
    renderList(upArr);
}

downbtn.onclick = () => {
    var downArr = cups.sort((a, b) => b.sales - a.sales)
    renderList(downArr);
}

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