Store first value of http request with rxjs but keep doing httprequest

Question

With RXJS library : I need to store values from the FIRST http request, but keep doing other http request on demand.

I have done this code so far, and that is working. But I think there is a more elegant way.

const Rx = require("rxjs");
let numHttp = 0;
const httpRequest = () => {
 let a = [];
 numHttp = numHttp + 1;
 for (let i = 0; i < 10; ++i) {
 a.push({ num: i, http: numHttp });
 };
 return new Rx.BehaviorSubject(a)
 .do(a => {
 console.log("antoher http request");
 if (getC.getValue() === undefined) {
 getC.next(a)
 }
 })
 // .do(n => { if (getB.) getB.next(n) })
}
const getB = () => {
 const a = new Rx.BehaviorSubject();
 return a
};
getC = getB();
httpRequest().subscribe(d => d);
httpRequest().subscribe(d => d);
getC.subscribe(data => console.log('cache', data))
httpRequest().subscribe(d => d);
httpRequest().subscribe(d => d);

Answer 1

It is really hard to solve the problem since the question is not providing all the necessary details.

Assuming you have a factory for your Http observable (call it createHttpObservable()) you may do something like this:

const observable = createHttpObservable()
 // Share the stream of events across all the subscribers.
 .publishReplay(1)
 .refCount()
 // Use `.scan()` against event stream (similarly to how we `.reduce()` against an array).
 .scan(
 (history, currentValue, valueIndex) => {
 history.push({ num: valueIndex, httpNum: currentValue });
 return history;
 },
 []
 )
 // Take the last event from the `history`
 .map(history => history[history.length - 1].httpNum)
 // Arbitrarily use `.do` for side effects.
 .do(console.log);
// Subscribe wherever you need.
observable.subscribe();
observable.subscribe();
observable.subscribe();

Here's a related, but not quite the same exact plunkr.

You can have more custom logic in the .scan() block, but frankly, I have no idea what are you trying to achieve and why is the first Http request's results are of any special interest.