<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
    </head>
    <body>
        <select name="" id="">
            <option value="0">请选择销量范围</option>
            <option value="1">&lt100</option>
            <option value="2">100~500</option>
            <option value="3">&gt500</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
                select.onchange = function(){
            	var index = select.selectedIndex;

            	function show(arr){
                	let list = ''; 
                	arr.forEach(function(v){
                		list += `<li>${v.name}</li>`
                	})
                	ul.innerHTML = list;
            	}
            	function choice(cups,index){
                	let resArr = cups.filter(function(v){
                    	if(index == 1){
                        	return v.sales < 100;
                    	}else if(index == 2){
                        	return v.sales >=100 && v.sales <=500;
                    	}else if(index == 3){
                        	return v.sales >500;
                    	}
                	})
                	return resArr;
           		}
           		show(choice(cups,index));

            }
        </script>
    </body>
</html>