<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
    </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
			const innerFn = ()=>{
			  let htmlStr = ''
			  cups.forEach(item => {
				htmlStr += `<li>${item.name}</li>`
			  })
			  ul.innerHTML = htmlStr
			}
			const fn = (num)=>{
			  cups = cups.sort((a, b) => a.sales > b.sales ? num : -num)
			  innerFn()
			}
			upbtn.onclick = function () {
			  fn(1)
			}
			downbtn.onclick = function () {
			  fn(-1)
			}
			innerFn()
        </script>
    </body>
</html>