发布订阅模式

//node事件模块
function Event () {
    this.cacheEvent = {}
}
//添加订阅事件
Event.prototype.on = function (type, handle) {
    if (!this.cacheEvent[type]){
        this.cacheEvent[type] = [handle]
    } else {
        this.cacheEvent[type].push(handle)
    }
}
//执行订阅事件
Event.prototype.emmit = function () {
    const type = arguments[0]
    const arg = Array.prototype.slice.call(arguments, 1)
    if (this.cacheEvent[type]) {
        for(let i = 0; i < this.cacheEvent[type].length; i++){
            this.cacheEvent[type][i](...arg)
            if (this.cacheEvent[type][i].flag){
                this.cacheEvent[type].splice(i,1)
            }
        }
     }
}
//删除订阅事件
Event.prototype.remove = function  (type, handle) {
    this.cacheEvent[type] = this.cacheEvent[type].filter(item => {
        return item !== handle
    })
}
//清空订阅事件
Event.prototype.empty = function (type) {
    this.cacheEvent[type] = []
}
//执行一次订阅事件
Event.prototype.once = function (type, handle) {
    handle.flag = true
    if (!this.cacheEvent[type]){
        this.cacheEvent[type] = [handle]
    } else {
        this.cacheEvent[type].push(handle)
    }
}