Understanding Operators

RxJS operators are a set of functions for transforming, composing, and controlling Observable data streams.

Operators are usually used in combination with several others, and this is where the "pipeline" comes in.

• What is RxJS Pipeline

In RxJS, operators fall into the following categories

List of categories

• Transformation Operators
• Filtering Operators
• Combination Operators
• Utility Operators
• Conditional Operators
• Error Handling Operators
• Multicasting Operators

Each category contains a number of useful operators. See each category for details.

List of Operators

For a detailed description of each operator, click on the link to browse.

List of Operator categories

Category	Operator	Description
Transformation	map	Converts each value
	scan	Accumulate values and output intermediate results
	reduce	Accumulate all values and output only the final result
	pairwise	Processes two consecutive values in pairs
	groupBy	Grouping streams by key
	mergeMap	Parallel execution of asynchronous processing
	switchMap	Execute only the latest asynchronous processing (cancel older processing)
	concatMap	Execute asynchronous processes sequentially
	exhaustMap	Ignore new processes during execution
	expand	Recursively expand results
	buffer	Publish values in an array
	bufferTime	Publish values at specified time intervals
	bufferCount	Publish values in batches of specified number of values
	bufferWhen	Buffering with dynamically controlled end conditions
	bufferToggle	Buffering with independent control of start and end
Filtering	filter	Only let through values that match the condition
	take	Get only the first N values
	takeLast	Get the last N values
	takeWhile	Get values while the condition is met
	skip	Skip the first N values
	skipLast	Skip the last N values
	skipWhile	Skip values while the condition is satisfied
	skipUntil	Skip values until another Observable fires
	first	Get the first value or the first value satisfying a condition
	last	Get the last value or the last value that satisfies the condition
	elementAt	Get the value at a given index
	find	Find the first value that satisfies a condition
	findIndex	Get the index of the first value that satisfies the condition
	debounceTime	Issue the last value if no input is received for a specified time
	throttleTime	Pass through the first value and ignore the new value for the specified time
	auditTime	Issue last value after specified time
	audit	Issue last value with custom Observable to control period
	sampleTime	Sample latest value at specified time interval
	ignoreElements	Ignore all values and only pass through completions/errors
	distinct	Remove all duplicate values (output only unique values)
	distinctUntilChanged	Remove consecutive duplicate values
	distinctUntilKeyChanged	Detect only changes in specific properties of an object
Combination (Pipeable)	concatWith	Join other Observables in sequence after completion
	mergeWith	Combine multiple Observables simultaneously
	combineLatestWith	Combine the latest value of each Observable
	zipWith	Pair values in corresponding order
	raceWith	Adopt only the first Observable that fires
	withLatestFrom	Append other latest values to the main stream
	mergeAll	Flatten Higher-order Observables in parallel
	concatAll	Flatten Higher-order Observable in sequence
	switchAll	Switch to the latest Higher-order Observable
	exhaustAll	Ignore new Higher-order Observable during execution
	combineLatestAll	Combines the latest values of all internal Observables
	zipAll	Pair the corresponding values of each internal Observable
Utility	tap	Perform side effects (e.g., log output)
	finalize	Perform post-processing on completion or error
	delay	Delay all values for a specified time
	delayWhen	Delay each value dynamically with a separate Observable
	timeout	Issue an error if a value does not arrive within a specified time
	takeUntil	Retrieve values until another Observable issues a value
	retry	Retry up to specified number of times on error
	repeat	Repeat a specified number of times after completion
	startWith	Adds an initial value to the beginning of the stream
	toArray	Publish all values together in an array
	materialize	Convert a notification to a Notification object
	dematerialize	Convert the Notification object back to a normal notification
	observeOn	Use the scheduler to control when values are published
	subscribeOn	Use the scheduler to control when to start subscribing
	timestamp	Add a timestamp to each value
Conditional	defaultIfEmpty	If no value is available, issue default value
	every	Determine if all values satisfy the condition
	isEmpty	Determines if no value was issued
Error Handling	catchError	Catch errors and perform fallback processing
	retry	Retry a specified number of times on error
	retryWhen	Retry with custom conditions
Multicasting	share	Share Observable among multiple subscribers
	shareReplay	Cache the latest N values and replay them to new subscribers