javaScript设计模式---（观察者模式）

// 观察者模式
// 第一步 模拟一系列依赖Observer
function ObserverList () {
    this.ObserverList = []
}
ObserverList.prototype.add = function (obj) {
    this.ObserverList.push(obj)
}
ObserverList.prototype.Empty = function () {
    this.ObserverList = []
}
ObserverList.prototype.Count = function () {
    return this.ObserverList.length
}
ObserverList.prototype.get = function (index) {
    if (index >= 0 && index < this.ObserverList.length) {
        return this.ObserverList[index]
    }
}
ObserverList.prototype.insert = function (index, obj) {
    var pointer = -1;
    if (index === 0) {
        this.ObserverList.unshift(obj)
        pointer = index
    } else if (index === this.ObserverList.length) {
        this.ObserverList.push(obj)
        pointer = index
    }
    return pointer
}
ObserverList.prototype.IndexOf = function (obj, startIndex) {
    let i = startIndex, pointer = -1;
    while (i < this.ObserverList.length) {
        if (obj = this.ObserverList[i]) {
            pointer = i
        }
        i++
    }
    return pointer
}
ObserverList.prototype.RemoveIndexAt = function (index) {
    if (index === 0) {
        this.ObserverList.shift()
    } else if (index === this.ObserverList.length){
        this.ObserverList.pop()
    }
}
// 使用extension拓展对象
function extend (obj, extension) {
    for (var key in obj) {
        extension[key] = obj[key]
    }
}

// 模拟目标(Subject)和在观察者列表上添加、删除或通知观察者
function Subject () {
    this.observers = new ObserverList()
}
Subject.prototype.AddObserver = function (observer) {
    this.observers.add(observer)
}
Subject.prototype.RemoveObserver = function (observer) {
    this.observers.RemoveIndexAt(this.observers.IndexOf(observer, 0))
}
Subject.prototype.Notify = function (context) {
    var observerCount = this.observers.Count()
    for (let i = 0; i < observerCount; i++) {
        this.observers.get(i).Update(context)
    }
}

 

后续继续学习~~~