Answer
mergeMap runs all inner observables concurrently. It is ideal for batch operations or parallel API calls, unlike switchMap which cancels previous executions.
Quick Answer
mergeMap subscribes to each inner Observable immediately as outer values arrive, running all concurrently without cancellation. Unlike switchMap (cancels previous), mergeMap keeps all in-flight. Use for parallel operations where all results are needed: upload multiple files simultaneously, process multiple items independently. Caution: no ordering guarantee, unlimited concurrency can overwhelm servers.
S
SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ