题解 | #数组排序#

     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');         
	 upbtn.onclick=function(){             
	 	cups.sort(upMethod);
	 	appendMethod();           
		} 
	 downbtn.onclick=function(){              
	 	cups.sort(downMethod);
	 	appendMethod();      
	}
	 function appendMethod(){
	 //注意每次增加节点前需要将原来的内容清空
	 	ul.innerHTML='';
	 	for(let val of cups){
	 	let li=document.createElement('li');            
	 	let text=document.createTextNode(val.name);
	 	li.appendChild(text);
	 	ul.appendChild(li);
	 }          
	 function upMethod(a,b){
	 	if(a.sales>b.sales){                   
		 return 1           
	 	}else{
	 	return -1
	 	}          
	 }          
	 function downMethod(a,b){
	 	if(a.sales>b.sales){
	 	return -1
	 	}else{
	 	return 1
	 	}            
	 }