operators.md

Operators

Operators are functions of the form: type Op<T, R> = (src: ReadableStream<T>) => ReadableStream<R> This only requires ReadableStream to be implemented/available with getReader support.

Operator Categories

Transformation Operators

Transform each value or the entire stream structure:

• map - Transform each value through a function
• mapSync - Synchronous transformation for better performance
• scan - Accumulate values and emit intermediate results
• reduce - Accumulate values and emit only the final result
• switchMap - Map to streams, switch to latest (with cancellation)
• concatMap - Map to streams, concatenate sequentially
• mergeMap - Map to streams, merge concurrently
• exhaustMap - Map to streams, ignore new while active
• switchAll - Flatten stream of streams, switch to latest
• concatAll - Flatten stream of streams sequentially
• mergeAll - Flatten stream of streams concurrently
• exhaustAll - Flatten stream of streams, ignore new while active
• pairwise - Emit previous and current values as pairs

Filtering Operators

Filter or limit the values that pass through:

• filter - Filter values with a predicate
• distinctUntilChanged - Remove consecutive duplicates
• distinctUntilKeyChanged - Remove consecutive duplicates by key
• distinct - Remove duplicate values globally
• first - Take first value (optionally matching predicate)
• last - Take last value (optionally matching predicate)
• take - Take first N values
• takeUntil - Take until another stream emits
• takeWhile - Take while predicate is true
• skip - Skip first N values
• skipWhile - Skip while predicate is true
• ignoreElements - Ignore all values, preserve completion

Timing Operators

Control the timing of emissions:

• debounceTime - Emit latest value after quiet period
• throttleTime - Limit emission rate
• delay - Delay all emissions by specified time
• timeout - Error if no emission within duration

Buffering Operators

Collect and group values:

• buffer - Buffer into arrays of specified size
• startWith - Prepend values to stream

Utility Operators

Observe, handle errors, and control flow:

• tap - Observe values without modification
• on - Attach lifecycle callbacks
• catchError - Handle errors with fallback stream
• schedule - Control emission timing with scheduler
• through - Use native TransformStream
• withLatestFrom - Combine with latest from other stream
• defaultIfEmpty - Provide default for empty streams
• count - Count values (optionally with predicate)
• bridge - Bridge to external stream systems