4.4.1、join

  1. var arr = ["html","css","javascript"];
  2. var b = arr.join();
  3. console.log(typeof b);
  4. console.log(arr.join("丨"))                  //  html丨css丨JavaScript

4.4.2、data

  1.  var data = {
  2.             country:"美国",
  3.             year:1994,
  4.             story:"犯罪"
  5.         }
  6.         //  美国丨1994丨犯罪
  7.         var arr = []
  8.         for(var i in data){
  9.            arr.push(data[i])
  10.         }
  11.         var str = arr.join("丨");
  12.         console.log(str);                   //  美国丨1994丨犯罪

4.4.3、根据年龄升序/降序（sort）
  1.        var students = [
  2.             {name:"zhang",age:20},
  3.             {name:"li",age:18},
  4.             {name:"wang",age:9},
  5.             {name:"chen",age:14},
  6.             ]
  7.       // 根据年龄升序
  8.             var result = students.sort((a,b)=>{
  9.             return a["age"]-b["age"];
  10.             })
  11.             console.log(result)
  12.      // 根据年龄降序
  13.             // var result = students.sort((a,b)=>{
  14.             // return b["age"]-a["age"];
  15.             // })
  16.             // console.log(result)

4.4.4、美团外卖排序
  1. <button id="like">通过好评数排序</button>
  2. <button id="price">通过价格排序</button>
  3.     <script>
  4.         var like = document.getElementById("like");
  5.         var sales = [
  6.             {name:"张三",like:60,distance:1000,price:10},
  7.             {name:"张三",like:30,distance:100,price:40},
  8.             {name:"张三",like:20,distance:500,price:6},
  9.         ]
  10.         /*升序*/ 
  11.         function addOrder(arr,value){
  12.             if(Array.isArray(arr)){
  13.                 var res = arr.sort((a,b)=>{
  14.                 return a[value]-b[value];
  15.             })
  16.             return res;
  17.             }else{
  18.                 return null;
  19.             }
  21.         }
  22.         like.onclick = function(){
  23.             console.log(addOrder(sales,"like"))
  24.         }
  25.         price.onclick = function(){
  26.             console.log(addOrder(sales,"price"))
  27.          }