Vue学习第四天（计算属性computed操作）

喜欢ヅ旅行 2022-12-18 00:50 44阅读 0赞

<!DOCTYPE html>
    <html lang="en">
    <head>
      <meta charset="UTF-8">
      <title>Title</title>
    </head>
    <body>
    <div id="app">
        总价格为：{
       {AutoPrice3}}
    </div>
    <script src="../js/vue.js"></script>
    <script>
      const app = new Vue ({
        el : '#app',
        computed:{
          AutoPrice:function(){
            let sumPrice=0;
            for(let i=0;i<this.books.length;i++){
              sumPrice+=this.books[i].price;
            }
             return sumPrice;
           },
            //多种for循环
            //for(let i in this.books)
            //for(let book of this.books)
          AutoPrice2: function(){
              let sumPrice=0;
              for(let i in this.books){
                sumPrice+=this.books[i].price;
              }
              return sumPrice*10;
          },
    
          AutoPrice3: function(){
            let sumPrice=0;
            for(let book of this.books){
              sumPrice+=book.price;
            }
            return sumPrice;
          }
    
        },
        data: {
          books:[
            {id:1,name:'小说1',price:119},
            {id:2,name:'小说2',price:130},
            {id:3,name:'小说3',price:200}
          ]
         }
      })
    </script>
    </body>
    </html>

# 02：get  和set操作 #

其实我们在使用 computed操作的时候，是自动调用了get的方法，并且computed相比较method是有缓存的

<!DOCTYPE html>
    <html lang="en">
    <head>
      <meta charset="UTF-8">
      <title>Title</title>
    </head>
    <body>
    <div id="app">
        {
       {fullName}}
    </div>
    <script src="../js/vue.js"></script>
    <script>
      const app = new Vue ({
        el : '#app',
        data: {
          firstName: 'FirstName',
          lastName: 'lastName'
         },
        computed: {
          fullName: {
            set:function (newValue){
              console.log("--------set------------");
              console.log(newValue);
              let names=newValue.split(" ");
              console.log(names);
              this.firstName=names[0];
              this.lastName=names[1];
            },
            get: function(){
              return this.firstName+"--------"+this.lastName
            }
          }
        }
        //computed和methods区别
        //methods方法，方法掉几次就会执行几次方法，效率比较低下
        //computed函数：只要 调的元素值不会发生变化，只会执行一次。但当值发生改变的时候，会重新调用一次该函数
        //computed 效率高，会有缓存的原因存在
      })
    </script>
    </body>
    </html>