js实现购物车计算的方法

<script>export default {    data() {        return {            count:0,            //所有商品的数量和            shopCarList: [],    //所有商品            selectList:[]       //已选择的商品         }    },    computed: {        //选择的合计价格        selectPrice(){            return this.selectList.reduce((total,item,index)=>{                return total+item.quantity*(item.activityPrice || item.price);            },0)        },        //选择的合计数量        selectNum(){            return this.selectList.reduce((total,item,index)=>{                return total+item.quantity;            },0)        },        //是否全选        isSelecetAll(){            return this.shopCarList.every(item=>{                return item.shopSelect===true            })        }    },    methods: {        //增加        increment(itm){            itm.quantity<itm.stock?itm.quantity++:'';        },        //减少        decrement(itm){            itm.quantity>1?itm.quantity--:''        },        //全选点击        allChooseHandle(){            this.initSelectAll(!this.isSelecetAll);        },        //商品单选点击        productChooseHandle(itm,index){            let productFlag = !itm.productSelect;            this.$set(itm,'productSelect',productFlag);             let shopFlag = this.shopCarList[index].products.every(i=>{                return i.productSelect===true;            })            this.$set(this.shopCarList[index],'shopSelect',shopFlag);            this.getSelected();        },        //店铺单选点击        shopChooseHandle(item,index){            let Flag = !item.shopSelect;            this.$set(item,'shopSelect',Flag);            item.products.forEach((itm,idx)=>{                this.$set(itm,'productSelect',Flag);            })            this.getSelected();        },        //获取已选商品        getSelected(){            let tempArr = [];            this.shopCarList.forEach((item,index)=>{                item.products.forEach((itm,idx)=>{                    if(itm.productSelect){                        tempArr.push(itm);                    }                })            })            this.selectList = tempArr;        },        //是否全选初始化        initSelectAll(Flag){            this.shopCarList.forEach((item,index)=>{                this.$set(item,'shopSelect',Flag);                item.products.forEach((itm,idx)=>{                    this.$set(itm,'productSelect',Flag);                })            })            this.getSelected();        },        //获取购物车列表        getCarList(){            return this.$api.personal.getCarList().then(res=>{                if(res.result==='000'){                    //过期商品数                    let expiredNum = 0;                    res.data.expiredList.forEach(item=>{                        item.products.forEach(itm=>{                            expiredNum += itm.quantity                        })                    })                    //有效商品数量                    this.count = res.data.count - expiredNum;                    this.shopCarList = res.data.shopCarList;                    return Promise.resolve()                }            })        },        //删除点击        delCarList(itm,index,idx){            this.$api.personal.delCarList( [itm.carId] ).then(res=>{                if(res.result==='000'){                    this.count  -= itm.quantity;                    this.shopCarList[index].products.splice(idx,1);                    if(this.shopCarList[index].products.length===0){                        this.shopCarList.splice(index,1);                    }                    this.getSelected();                }            })        },    },    created() {        this.getCarList().then(()=>{            this.initSelectAll(true);        });    },};</script>