const Observable = Rx.Observable;

​

let counter = 1;

const RECACHE_INTERVAL = 1000;

​

function mockDataFetch() {

  return Observable.of(counter++)

    .delay(200);

}

​

let source = Observable.defer(() => {

  const now = (new Date()).getTime();

​

  return mockDataFetch()

    .map(response => {

      return {

        'timestamp': now,

        'response': response,

      };

    });

});

​

let updateRequest = source

  .publishReplay(1)

  .refCount()

  .concatMap(value => {

    if (value.timestamp + RECACHE_INTERVAL > (new Date()).getTime()) {

      return Observable.from([value.response, null]);

    } else {

      return Observable.of(value.response);

    }

  })

  .takeWhile(value => value);

​

​

setTimeout(() => updateRequest.subscribe(val => console.log("Response 0:", val)), 0);

​

setTimeout(() => updateRequest.subscribe(val => console.log("Response 50:", val)), 50);

​

setTimeout(() => updateRequest.subscribe(val => console.log("Response 200:", val)), 200);

​

setTimeout(() => updateRequest.subscribe(val => console.log("Response 1200:", val)), 1200);

​

setTimeout(() => updateRequest.subscribe(val => console.log("Response 1300:", val)), 1300);

​

setTimeout(() => updateRequest.subscribe(val => console.log("Response 1500:", val)), 1500);

​

setTimeout(() => updateRequest.subscribe(val => console.log("Response 3500:", val)), 3500);

​