[Solved] Given the code below, what will be logged to the console? const source$ = of('A', 'B', 'C'); source$.pipe( switchMap(letter => of(letter + '1', letter + '2')) ).subscribe(console.log); | Angular

Angular - RxJS Operators

Given the code below, what will be logged to the console?

const source$ = of('A', 'B', 'C');
source$.pipe(
  switchMap(letter => of(letter + '1', letter + '2'))
).subscribe(console.log);

A"C1" and "C2" only

B["A1", "A2", "B1", "B2", "C1", "C2"]

C"A1" and "A2" only

DError: switchMap requires an observable

Step-by-Step Solution

Solution:

Step 1: Understand source observable emissions
The source$ emits 'A', then 'B', then 'C' synchronously.
Step 2: Apply switchMap to each emission
For each letter, switchMap maps to an observable emitting letter+'1' and letter+'2'. Since source$ emits synchronously, switchMap cancels previous inner observables when a new outer emission occurs, so only the last inner observable's values "C1" and "C2" are emitted.
Step 3: Resulting output
Only "C1" and "C2" are logged to the console.
Final Answer:
"C1" and "C2" only -> Option A
Quick Check:
switchMap cancels previous inner observables, so only last inner observable outputs [OK]

Quick Trick: switchMap cancels previous inner observables, outputs only latest inner values [OK]

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