<template>
  <div>
    <table>
      <tr>
        <th><input type="checkbox" v-model="selectAll" />全選/全不選</th>
        <th v-for="(item, index) in titles" :key="index">{{ item }}</th>
      </tr>
      <tr v-for="(item, index) in books" :key="item.name">
        <td><input type="checkbox" v-model="item.select" /></td>
        <td>{{ index }}</td>
        <td>{{ item.name }}</td>
        <td>{{ item.date }}</td>
        <td>¥{{ item.price.toFixed(2) }}</td>
        <td>
          <button @click="redu(index)">-</button>
          {{ item.num }}
          
 
<button @click="add(index)">+</button>
        </td>
        <td><button @click="del(index)">移除</button></td>
      </tr>
      <tr>
        <td colspan="7" style="text-align: left">總價格為:{{ total }}</td>
      </tr>
    </table>
  </div>
</template>

<script>
export 
 
default {
  data() {
    return {
      titles: ["編號", "書籍名稱", "出版日期", "價格", "數量", "操作"],
      books: [
        {
          name: "演算法導論",
          date: "2006-9",
          price: 85,
          num: 1,
          select: true,
        },
        {
          name: "UNIX程式設計藝術",
          date: "2006-2",
          price: 
 
59,
          num: 1,
          select: true,
        },
        {
          name: "Vue程式設計",
          date: "2008-10",
          price: 35,
          num: 1,
          select: true,
        },
        {
          name: "頸椎康復",
          date: "2006-3",
          price: 129,
          num: 1,
          select: true,
        },
      ],
    };
  },
  computed: {
    total() {
      let ret = this.books.reduce((pre, cur) => {
        return cur.price * cur.num + pre;
      }, 0);
      return "¥" + ret.toFixed(2);
    },
    selectAll: {
      get() {
        for (let i = 0; i < this.books.length; i++) {
          if (!this.books[i].select) {
            return false;
          }
        }
        return true;
      },
      set(newVal) {
        this.books.forEach((item) => {
          item.select = newVal;
        });
      },
    },
  },
  methods: {
    add(i) {
      if (!this.books[i].select) {
        alert("你還沒做出選擇");
        return;
      }
      this.books[i].num++;
    },
    redu(i) {
      if (!this.books[i].select) {
        alert("你還沒做出選擇");
        return;
      }
      this.books[i].num > 1 ? this.books[i].num-- : "";
    },
    del(i) {
      if (!this.books[i].select) {
        alert("你還沒做出選擇");
        return;
      }
      this.books.splice(i, 1);
    },
  },
};
</script>
 
<style lang = "less" scoped>
table {
  border-collapse: collapse;
  margin: 100px auto;
}
table,
td,
th {
  border: 1px solid #000;
}
td,
th {
  padding: 10px;
}
</style>