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09-综合练习.md

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综合前面的知识，需要通过一个小demo来串联起知识。

如图所示：

点击“+”按钮，总价增加，点击“-”按钮总价减少，点击移除，移除当列。

1. 目录结构

2. index.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>综合练习</title>
  <link rel="stylesheet" href="./css/style.css">
</head>
<body>
<div id="app">
  <table>
    <thead>
    <th>&nbsp;</th>
    <th>书籍名称</th>
    <th>出版日期</th>
    <th>价格</th>
    <th>购买数量</th>
    <th>操作</th>
    </thead>
    <tbody>
    <tr v-for="(book,index) in books">
      <td>{{index}}</td>
      <td>{{book.name}}</td>
      <td>{{book.beginDate}}</td>
      <td>{{book.price | showPrice}}</td>
      <td>
        <button @click="decrement(index)" :disabled="book.count<=1">-</button>
        {{book.count}}
        <button @click="increment(index)">+</button>
      </td>
      <td>
        <button @click="remove(index)">移除</button>
      </td>
    </tr>
    </tbody>
  </table>
  <h3>总价：{{totalPrice | showPrice}}</h3>
</div>
<script src="../js/vue.js"></script>
<script src="./js/main.js"></script>
</body>
</html>

3.main.js

const app = new Vue({
  el: '#app',
  data: {
    books: [
      {
        name: "《算法导论》",
        beginDate: "2006-9",
        price: 85.00,
        count: 1
      },
      {
        name: "《UNIX编程艺术》",
        beginDate: "2006-2",
        price: 59.00,
        count: 1
      },
      {
        name: "《编程大全》",
        beginDate: "2008-10",
        price: 39.00,
        count: 1
      },
      {
        name: "《代码大全》",
        beginDate: "2006-3",
        price: 128.00,
        count: 1
      },
    ]
  },
  methods: {
    increment(index){
      this.books[index].count++
    },
    decrement(index){
      this.books[index].count--
    },
    remove(index){
      this.books.splice(index,1)
    }
  },
  computed: {
    totalPrice(){
      return this.books.map(book => book.price*book.count)
          .reduce((preValue,currentValue) => preValue+currentValue)
    }
  },
  filters: {
    showPrice: function(price){
      console.log(typeof price);
      let priceStr = price.toFixed(2)
      console.log(priceStr);
      return "￥" + priceStr
    }
  }
})

4. style.css

table{
  border: 1px;
  border-collapse: collapse;
  border-spacing: 0;
}
th,td{
  padding: 8px 16px;
  border: ipx solid #e9e9e9;
  text-align: left;
}
th{
  background-color: #f7f7f7;
  color: #5c6b77;
  font-weight: 600;
}

filter、map、reduce

// 1.filter过滤函数
const nums = [2,3,5,1,77,55,100,200]
//要求获取nums中大于50的数
//回调函数会遍历nums中每一个数，传入回调函数，在回调函数中写判断逻辑，返回true则会被数组接收，false会被拒绝
let newNums = nums.filter(function (num) {
  if(num > 50){
    return true;
  }
  return false;
 })
 //可以使用箭头函数简写
//  let newNums = nums.filter(num => num >50)
 console.log(newNums);
// 2.map高阶函数
// 要求将已经过滤的新数组每项乘以2
//map函数同样会遍历数组每一项，传入回调函数为参数，num是map遍历的每一项，回调函数function返回值会被添加到新数组中
let newNums2 = newNums.map(function (num) {
  return num * 2
 })
 //简写
//  let newNums2 = newNums.map(num => num * 2)
console.log(newNums2);
// 3.reduce高阶函数
//要求将newNums2的数组所有数累加
//reduce函数同样会遍历数组每一项，传入回调函数和‘0’为参数，0表示回调函数中preValue初始值为0，回调函数中参数preValue是每一次回调函数function返回的值，currentValue是当前值
//例如数组为[154, 110, 200, 400],则回调函数第一次返回值为0+154=154，第二次preValue为154，返回值为154+110=264，以此类推直到遍历完成
let newNum = newNums2.reduce(function (preValue,currentValue) {
  return preValue + currentValue
 },0)
//简写
// let newNum = newNums2.reduce((preValue,currentValue) => preValue + currentValue)
console.log(newNum);

//三个需求综合
let n = nums.filter(num => num > 50).map(num => num * 2).reduce((preValue,currentValue) => preValue + currentValue)
console.log(n);