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//观察者模式实现异步function create(fn){       let ret = false    return ({    next, complete, error })=>{           function nextFn(...args){               if(ret){                   return            }            next(...args)        }        function completeFn(...args){               complete(...args)            ret = true        }        function errorFn(...args){               error(...args)        }        fn({               next: nextFn,            complete: completeFn,            error: errorFn        })        return ()=>(ret = true)    }}/** *观察者 * observerable 等于（{ next, complete, error }）=>{ *      function nextFn ... *      function complete ... *      function errorFn ... *      (observer=>{ *          setTimeout(()=>{ observer.next(1) }, 1000) *          observer.next(2) *          observer.complete(3) *      })() 执行 *      return ()=>( ret = true ) * } * */let observerable = create(observer => {       setTimeout(()=>{           observer.next(1)    }, 1000)    observer.next(2)    observer.complete(3)})/** * 被观察者 */const subject = {       next: value=>{           console.log(value)    },    complete: console.log,    error: console.log}let unsubscribe = observerable(subject)

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