Use this operator in case you want to release multiple values on every source one. On every message of a source Observable, transforming function is expected to return an Observable that will contain values that'll be pushed through resulting Observable.
Unlike flatMap, a new outputted Observable is acknowledged immediately and sending new Observable will cancel reading the previous one.
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import{ Observable, switchMap }from'@hullo/core';
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let i =0;
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newObservable(observer =>{
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setInterval(()=>{
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observer.next({ i: i++, t: Date.now()});
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},1000);
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})
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.pipe(switchMap(
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({ i, t })=>observable(observer =>{
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setInterval(()=>{
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observer.next(`${i}${Date.now()- t}`);
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},100);
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})
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))
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.subscribe({
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next: v =>{console.log(v)}
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})
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/* Output
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0 107
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0 210
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0 314
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0 420
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0 524
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0 626
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0 726
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0 832
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0 934
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1 106
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1 211
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1 315
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1 420
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1 524
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1 629
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1 732
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1 837
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1 940
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2 106
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2 208
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2 313
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2 418
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2 520
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2 626
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2 726
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2 832
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2 933
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3 105
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3 205
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3 307
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3 408
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3 509
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3 609
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3 710
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3 816
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3 917
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*/
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In this example the time difference between Date.now() in source and Date.now in switchMap transformation function will never be greater than a second because that is the time source needs to push a new value which will then cause creation of next comparing times Observable.