index.ts

console.log('Hello World')

const callback = ()=>{
    console.log('Hello World')
}

const reminder =()=>{
    console.log('Time to drink water!')
}
const reminderCb = (cb:any)=>{
   cb()
}
const reminderCbAndTimerCb = (cb:any)=>{
   cb()
   setTimeout(() => {
    cb()
  }, 1000)
}
reminder()
reminderCb(()=>{console.log('Time to write code !')})
reminderCbAndTimerCb(()=>{console.log('Time to wtire code again and again')})


class Reminder {
  remind(cb:any){
    cb.next(1);
    cb.complete()
  }
}

const reminder1 = new Reminder();

reminder1.remind({
  next:(val:any)=>{
      console.log(val,'next')
  },
  complete:(val:any)=>{
      console.log(val)
  },
})

class Reminder2 {
  behavior:any;
  constructor(behavior:any){
    this.behavior = behavior
  }
  remind(cb:any){
    this.behavior(cb)
  }
}

const reminder2 = new Reminder2((cb:any )=>{
  cb.next(2);
  cb.complete();
})
reminder2.remind({
  next(val:any){
     console.log(val,'next2')
  },
  complete(val:any){
     console.log(val,'complete')
  },
})
//  Reminder => Observable
//  remind => subscribe
//  cb => observer
//  reminder => obs$
class Observable {
  behavior:any; // 或者_subscribe
  constructor(behavior:any){
    this.behavior = behavior
    // this._subscribe = subscribe 构造函数也可用subscribe
  }
  subscribe(observer:any){
    this.behavior(observer)
    // this._subscribe(observer)
  }
}

const obs$ = new Observable((observer:any)=>{
   observer.next(1);
   throw new Error(" ddd");
   observer.complete()
})

const observer = {
  next:(val:any) =>{
    console.log(val,'observer next')

  },
  error:(err:any)=>{
    console.log(err,'err')
  },
  complete:()=>{
    console.log('complete')
  }
}
obs$.subscribe(observer)
// 官方 Observable 的 subscribe 可以传入一个函数进去，这样的话写起来会清爽很多，我们也来实现一下

class OfficialObservable {
  _subscribe:any; // 或者_subscribe
  constructor(subscribe:any){
    this._subscribe = subscribe
    // this._subscribe = subscribe 构造函数也可用subscribe
  }
  subscribe(observer:any):any{
    const defaultObserver = {
      next:()=>{
        console.log('next')
      },
      err:()=>{
        console.log('err')
      },
      complete:()=>{
        console.log('complete')
      }
    }
    if(typeof observer === 'function'){
      return this.subscribe({...defaultObserver,next:observer})
    }
    return this._subscribe({...defaultObserver,...observer})
  }
}