As the demo shows, as the title said
const { combineLatest, interval, of } = rxjs;
const { first, last, sample, take, withLatestFrom } = rxjs.operators;
const numbers = interval(1000);
const takeFourNumbers = numbers.pipe(take(4));
takeFourNumbers.subscribe(x => console.log('Next: ', x));
setTimeout(()=>{
console.log('how can we get the latest value which is 1?');
takeFourNumbers.pipe(first()).subscribe(v=>console.log(v,'actual get'))
},2500)
// Logs:
// Next: 0
// Next: 1
// how can we get the latest value which is 1?
// Next: 2
// 0 actual get
// Next: 3<script src="https://cdn.jsdelivr.net/npm/rxjs@7.5.5/dist/bundles/rxjs.umd.js"></script>In my case, I just want to get the latest value and do a one-time job. How can I do it?
I am thinking if we have an operator like takeLatest() or latest()? But I didn't find anyone.
The problem boils down to sharing provider(data source) or "Hot vs Cold" observables, you want the latest value to be shared across different subscriptions so you basically want a hot observable, Observable returned from interval operator is cold so you need to make it hot and doing so is quite simple:
const takeFourNumbers = numbers.pipe(take(4), shareReplay(1));
now it doesn't matter how many times you subscribe to it, all subscribers will share the value
edit: my bad, it should be shareReplay so that it gives you last emitted value as soon as you subscribe to it so now you should get 1 from that subscription inside setTimeout