vue3 写一段购物车

好的，下面是一个简单的 Vue 3 购物车示例代码：

<template>
  <div class="cart">
    <h2>购物车</h2>
    <div class="cart-items">
      <div class="cart-item" v-for="(item, index) in items" :key="index">
        <div class="cart-item__name">{{ item.name }}</div>
        <div class="cart-item__price">￥{{ item.price }}</div>
        <div class="cart-item__quantity">
          <button @click="decrease(index)">-</button>
          {{ item.quantity }}
          <button @click="increase(index)">+</button>
        </div>
        <div class="cart-item__subtotal">小计：￥{{ item.subtotal }}</div>
        <div class="cart-item__remove">
          <button @click="remove(index)">删除</button>
        </div>
      </div>
    </div>
    <div class="cart-summary">
      <div class="cart-summary__subtotal">商品总价：￥{{ subtotal }}</div>
      <div class="cart-summary__shipping">运费：￥{{ shipping }}</div>
      <div class="cart-summary__total">总价：￥{{ total }}</div>
    </div>
  </div>
</template>

<script>
export default {
  data() {
    return {
      items: [
        { id: 1, name: '商品1', price: 100, quantity: 1 },
        { id: 2, name: '商品2', price: 200, quantity: 2 },
        { id: 3, name: '商品3', price: 300, quantity: 3 }
      ],
      shipping: 10
    };
  },
  computed: {
    // 计算商品总价
    subtotal() {
      return this.items.reduce((acc, item) => acc + item.subtotal, 0);
    },
    // 计算总价
    total() {
      return this.subtotal + this.shipping;
    }
  },
  methods: {
    // 增加商品数量
    increase(index) {
      this.items[index].quantity++;
    },
    // 减少商品数量
    decrease(index) {
      if (this.items[index].quantity > 1) {
        this.items[index].quantity--;
      }
    },
    // 删除商品
    remove(index) {
      this.items.splice(index, 1);
    }
  },
  // 监听数据变化，重新计算小计
  watch: {
    items: {
      handler(val) {
        val.forEach(item => {
          item.subtotal = item.price * item.quantity;
        });
      },
      immediate: true,
      deep: true
    }
  }
};
</script>

<style>
.cart {
  border: 1px solid #ccc;
  padding: 10px;
}
.cart h2 {
  font-size: 24px;
  margin-bottom: 10px;
}
.cart-items {
  margin-bottom: 20px;
}
.cart-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid #ccc;
  padding: 10px 0;
}
.cart-item__name {
  font-size: 18px;
}
.cart-item__price {
  font-size: 18px;
}
.cart-item__quantity {
  display: flex;
  align-items: center;
}
.cart-item__quantity button {
  font-size: 18px;
  padding: 5px 10px;
  margin: 0 5px;
}
.cart-item__subtotal {
  font-size: 18px;
}
.cart-item__remove {
  font-size: 18px;
}
.cart-item__remove button {
  color: red;
  border: none;
  background-color: transparent;
  cursor: pointer;
}
.cart-summary {
  display: flex;
  justify-content: flex-end;
  align-items: center;
  font-size: 18px;
}
.cart-summary__subtotal {
  margin-right: 20px;
}
</style>

这个购物车示例包含了商品列表、小计、总价等功能。用户可以增加或减少商品数量，也可以删除某个商品。在数据变化时，小计和总价会自动重新计算。