<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
    </head>
    <body>
        <select name="" id="" onchange="handleSelectChange(this.value)">
            <option value="0">请选择销量范围</option>
            <option value="1"><100</option>
            <option value="2">100~500</option>
            <option value="3">>500</option>
        </select>
        <ul>
            <li>牛客logo马克杯</li>
            <li>无盖星空杯</li>
            <li>老式茶杯</li>
            <li>欧式印花杯</li>
        </ul>

        <script>
            var cups = [
                { type: 1, price: 100, color: 'black', sales: 60, name: '牛客logo马克杯' },
                { type: 2, price: 40, color: 'blue', sales: 100, 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 select = document.querySelector('select');
            var ul = document.querySelector('ul');
            // 补全代码
            function handleSelectChange(val) {
                switch(val) {
                    case '1': initUl(cups.filter(item => item.sales < 100)); break;
                    case '2': initUl(cups.filter(item => item.sales >= 100 && item.sales <= 500)); break;
                    case '3': initUl(cups.filter(item => item.sales > 500)); break;
                }
            }
            function initUl(array) {
                ul.innerHTML = '';
                for (let i = 0 ; i < array.length; i++) {
                    let liEl = document.createElement('li');
                    liEl.innerHTML = array[i].name;
                    ul.appendChild(liEl);
                }
            }
        </script>
    </body>
</html>