什么是计算属性？

计算属性的复杂操作

<div id="app">
  <h2>总价格: {{totalPrice}}</h2>
  <h2>总价格: {{totalPrice}}</h2>
  <h2>总价格: {{totalPrice}}</h2>
  <h2>总价格: {{totalPrice}}</h2>

  <h2>总价格: {{getTotalPrice()}}</h2>
  <h2>总价格: {{getTotalPrice()}}</h2>
  <h2>总价格: {{getTotalPrice()}}</h2>
  <h2>总价格: {{getTotalPrice()}}</h2>
</div>

<script src="../js/vue.js"></script>
<script>
  const app = new Vue({
    el: '#app',
    data: {
      books: [
        {id: 110, name: 'Unix编程艺术', price: 119},
        {id: 111, name: '代码大全', price: 105},
        {id: 112, name: '深入理解计算机原理', price: 98},
        {id: 113, name: '现代操作系统', price: 87},
      ]
    },
    methods: {
      getTotalPrice: function () {
        let result = 0
        for (let i=0; i < this.books.length; i++) {
          result += this.books[i].price
        }
        return result
      }
    },
    computed: {
      totalPrice: function () {
        let result = 0
        for (let i=0; i < this.books.length; i++) {
          result += this.books[i].price
        }
        return result

        // for (let i in this.books) {
        //   this.books[i]
        // }
        //
        // for (let book of this.books) {
        //
        // }
      }
    }
  })

?计算属性的setter和getter

<div id="app">
  <h2>{{fullName}}</h2>
</div>

<script src="../js/vue.js"></script>
<script>
  const app = new Vue({
    el: '#app',
    data: {
      firstName: 'Kobe',
      lastName: 'Bryant'
    },
    computed: {
      // fullName: function () {
      //   return this.firstName + ' ' + this.lastName
      // }
      // name: 'coderwhy'
      // 计算属性一般是没有set方法, 只读属性.
      fullName: {
        set: function(newValue) {
          // console.log('-----', newValue);
          const names = newValue.split(' ');
          this.firstName = names[0];
          this.lastName = names[1];
        },
        get: function () {
          return this.firstName + ' ' + this.lastName
        }
      },

      // fullName: function () {
      //   return this.firstName + ' ' + this.lastName
      // }
    }
  })
</script>