设计原则与设计模式

    //用promise说明SO
   function loadImg(src) {
        var promise = new Promise(function (resolve, reject) {
            var img = document.createElement('img')
            img.onload = function () {
                resolve(img)
            }
            img.onerror = function () {
                reject('图片加载失败')
            }
            img.src = src
        })
        return promise
    }

    var imgSrc = 'https://static.ahwgs.cn/wp-content/uploads/2018/12/XQXT_RUDC1YB0FUW.png';
    var result = loadImg(imgSrc)

    result
        .then(function (img) {
            console.log('img width',img.width)
            return img
        })
        .then(function (img) {
            console.log('img height',img.height)
        })
        .catch(function (err) {
            console.log(err);
        })

    //Car 父类
    class Car {
        constructor(number, name) {
            this.name = name;  //车信息
            this.number = number;  //车牌号
        }
    }

    //专车类
    class Zhuanche extends Car {
        constructor(number, name) {
            super(number, name);
            this.price = 2
        }
    }

    //快车类
    class Kuaiche extends Car {
        constructor(number, name) {
            super(number, name);
            this.price = 1
        }
    }

    //行程类
    class Trip {
        constructor(car){
            this.car = car
        }
        //显示车牌信息
        start(){
            console.log('行程开始.名称:'+this.car.name+',车牌号:'+this.car.number)
        }
        end(){
            console.log('行程结束.总计:'+this.car.price * 5)
        }
    }

    var car = new Kuaiche('皖A000001','大奔')
    var trip = new Trip(car);

    trip.start()
    trip.end()

// 车
    class Car {
        constructor(num) {
            this.num = num
        }
    }

    // 入口摄像头
    class Camera {
        shot(car) {
            return {
                num: car.num,
                inTime: Date.now()
            }
        }
    }

    // 出口显示器
    class Screen {
        show(car, inTime) {
            console.log('车牌号', car.num)
            console.log('停车时间', Date.now() - inTime)
        }
    }

    // 停车场
    class Park {
        constructor(floors) {
            this.floors = floors || []
            this.camera = new Camera()
            this.screen = new Screen()
            this.carList = {}
        }

        in(car) {
            // 获取摄像头的信息：号码 时间
            const info = this.camera.shot(car)
            // 停到某个车位
            const i = parseInt(Math.random() * 100 % 100)
            const place = this.floors[0].places[i]
            place.in()
            info.place = place
            // 记录信息
            this.carList[car.num] = info
        }

        out(car) {
            // 获取信息
            const info = this.carList[car.num]
            const place = info.place
            place.out()

            // 显示时间
            this.screen.show(car, info.inTime)

            // 删除信息存储
            delete this.carList[car.num]
        }

        emptyNum() {
            return this.floors.map(floor => {
                return `${floor.index} 层还有 ${floor.emptyPlaceNum()} 个车位`
            }).join('\n')
        }
    }

    // 层
    class Floor {
        constructor(index, places) {
            this.index = index
            this.places = places || []
        }

        emptyPlaceNum() {
            let num = 0
            this.places.forEach(p => {
                if (p.empty) {
                    num = num + 1
                }
            })
            return num
        }
    }

    // 车位
    class Place {
        constructor() {
            this.empty = true
        }

        in() {
            this.empty = false
        }

        out() {
            this.empty = true
        }
    }

    // 测试代码------------------------------
    // 初始化停车场
    const floors = []
    for (let i = 0; i < 3; i++) {
        const places = []
        for (let j = 0; j < 100; j++) {
            places[j] = new Place()
        }
        floors[i] = new Floor(i + 1, places)
    }
    const park = new Park(floors)

    // 初始化车辆
    const car1 = new Car('A1')
    const car2 = new Car('A2')
    const car3 = new Car('A3')

    console.log('第一辆车进入')
    console.log(park.emptyNum())
    park.in(car1)
    console.log('第二辆车进入')
    console.log(park.emptyNum())
    park.in(car2)
    console.log('第一辆车离开')
    park.out(car1)
    console.log('第二辆车离开')
    park.out(car2)

    console.log('第三辆车进入')
    console.log(park.emptyNum())
    park.in(car3)
    console.log('第三辆车离开')
    park.out(car3)