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What is the main difference between combineLatest and forkJoin in Angular RxJS?

easy🧠 Conceptual Q11 of 15
Angular - RxJS Operators
What is the main difference between combineLatest and forkJoin in Angular RxJS?
A<code>combineLatest</code> and <code>forkJoin</code> behave exactly the same.
B<code>combineLatest</code> waits for all sources to complete; <code>forkJoin</code> emits on every source emission.
C<code>combineLatest</code> emits values whenever any source emits; <code>forkJoin</code> emits once when all sources complete.
D<code>combineLatest</code> only emits once; <code>forkJoin</code> emits multiple times.
Step-by-Step Solution
Solution:

  1. Step 1: Understand combineLatest behavior

    combineLatest emits a new combined value whenever any source observable emits after all have emitted at least once.

  2. Step 2: Understand forkJoin behavior

    forkJoin waits for all source observables to complete and then emits a single combined array of their last emitted values.

  3. Final Answer:

    combineLatest emits on any change; forkJoin emits once after all complete. -> Option C

  4. Quick Check:

    combineLatest = live updates, forkJoin = final result [OK]
Quick Trick: combineLatest updates live; forkJoin waits for all done [OK]
Common Mistakes:
MISTAKES
  • Thinking forkJoin emits multiple times
  • Confusing combineLatest with forkJoin completion behavior
  • Assuming combineLatest waits for all to complete

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