shopdemo

import React, { Component } from 'react'
export default class shopDemo extends Component {
    state = {
        goods: [
            {
                id: 1,
                name: '商品1',
                price: 100,
                number: 0,
                money: 0
            },
            {
                id: 2,
                name: '商品2',
                price: 200,
                number: 0,
                money: 0
            },
            {
                id: 3,
                name: '商品3',
                price: 300,
                number: 0,
                money: 0
            }
        ],
        allprice: 0
    }
    // 校验所有的input是否选中
    changeAllSelect() {
        let inputAllMessage = document.getElementsByTagName('input')
        for (let i = 1; i < inputAllMessage.length; i++) {
            console.log(inputAllMessage);
            if (!inputAllMessage[i].checked) {
                return false;
            }
        }
        return true;
    }
    // 获取到所有的函数, 然后进行判断, 判断是否全选
    changeFunction() {
        let result = this.changeAllSelect()
        let allResultSelect = document.getElementById('all')
        if (result) {
            allResultSelect.checked = true
        } else {
            allResultSelect.checked = false
        }
    }
    // 减少商品的数量计算单价和总价
    reduceGoods(index) {
        if (this.state.goods[index].number <= 0) {
            return alert('不能再少了')
        } else {
            this.setState({
                goods: this.state.goods.map((item, ind) => {
                    if (index === ind) {
                        item.number--
                        item.money = item.number * item.price
                    }
                    return item
                }),
                allprice: this.state.allprice - this.state.goods[index].price
            })
        }
        if (this.state.goods[index].number == 0) {
            let idInput = document.getElementById(index)
            idInput.checked = false
        }
        this.changeFunction()
    }
    // 增加商品计算总价和改变商品的数量
    addGoods(index) {
        this.setState({
            goods: this.state.goods.map((item, ind) => {
                if (index === ind) {
                    item.number++
                    item.money = item.number * item.price
                }
                return item
            }),
            allprice: this.state.allprice + this.state.goods[index].price
        })
        if (this.state.goods[index].number > 0) {
            let idInput = document.getElementById(index)
            idInput.checked = true
        }
        this.changeFunction()
    }
    // 全选操作
    changeValue() {
        const getSelectValue = document.getElementById('all')
        let inputAllMessage = document.getElementsByTagName('input')
        if (getSelectValue.checked) {
            for (let i = 1; i < inputAllMessage.length; i++) {
                console.log(inputAllMessage);
                inputAllMessage[i].checked = true;
            }
            let allprice = 0
            for (let i = 1; i < inputAllMessage.length; i++) {
                if (inputAllMessage[i].checked) {
                    allprice += this.state.goods[i-1].money
                }
            }
            this.setState({
               allprice:  allprice
            })
        } else {
            for (let i = 1; i < inputAllMessage.length; i++) {
                console.log(inputAllMessage);
                inputAllMessage[i].checked = false;
            }
            this.setState({
                allprice:0
            })
        }
    }
    // 判断是否每一项都是全部被选中的状态
    checkedMessage(value){
        for(let i=1;i<value.length;i++){
            if(!value[i].checked){
                return false
            }
        }
        return true
    }
    // 点击选择单个商品时触发的函数
    everyChangeInputValue(){
        const inputChangeValues = document.getElementsByTagName('input')
        let checkResult = this.checkedMessage(inputChangeValues)
        if(checkResult){
            document.getElementById('all').checked = true
        }else{
            document.getElementById('all').checked = false
        }
    }
    // 页面配置
    render() {
        return (
            <div>
                <div>
                    全选<input type="checkbox" id='all' onClick={() => this.changeValue()} />
                </div>
                <div >
                    {
                        this.state.goods.map((item, index) => {
                            return <div key={index}>
                                <input type="checkbox" id={index} onClick={() => this.everyChangeInputValue()} />
                                <span>{item.name}</span>
                                <span>{item.price}</span>
                                <button onClick={() => this.reduceGoods(index)}>-</button>
                                <span>{item.number}</span>
                                <button onClick={() => this.addGoods(index)}>+</button>
                                <span>小计:{item.money}元</span>
                            </div>
                        })
                    }
                </div>
                <div>
                    总价：<span>{this.state.allprice}元</span>
                </div>
            </div>
        )
    }
}

效果图