pub/sub 这个应该⼤家⽤到最⼴的设计模式了，
class Event{
constructor(){
this.callbacks = {}
}
$off(name){
this.callbacks[name] = null
}
$emit(name, args){
let cbs = this.callbacks[name]
if (cbs) {
cbs.forEach(c=>{
c.call(this, args)
})
}
}
$on(name, fn){
(this.callbacks[name] || (this.callbacks[name] = [])).push(fn)
}
}
let event = new Event()
event.$on('event1', function(arg){
console.log('事件1',arg)
})
event.$on('event1', function(arg){
console.log('⼜⼀个时间1',arg)
})
event.$on('event2', function(arg){
console.log('事件2',arg)
})
event.$emit('event1',{name:'开课吧'})
event.$emit('event2',{name:'全栈'})
event.$off('event1')
event.$emit('event1',{name:'开课吧'})