面试题与答案

Multicasting is the process of broadcasting a single source Observable to multiple subscribers, preventing redundant work for shared operations.

Example:

const subject = new Subject(); observable.subscribe(subject);

'Cold' Observables start producing values only when a subscription is made, while 'Hot' Observables produce values even before any subscriptions.

Example:

Cold: const coldObservable = new Observable(...); Hot: const hotObservable = new Subject();

The 'debounceTime' operator is used to emit a value from an Observable only after a specified amount of time has passed without any new values being emitted.

Example:

const debouncedObservable = inputObservable.pipe(debounceTime(300));

Schedulers are used to control the execution context and timing of Observable operations, allowing you to control when and where certain code is executed.

Example:

const scheduledObservable = observable.pipe(delay(1000, asyncScheduler));

'finalize' is used to perform a specified action when an Observable completes, whether it completes normally or due to an error.

Example:

const finalizedObservable = observable.pipe(finalize(() => console.log('Observable completed')));

ReplaySubjects are similar to Subjects but can 'replay' a specified number of previously emitted values to new subscribers, ensuring they receive a specific history of values.

Example:

const replaySubject = new ReplaySubject(2); replaySubject.next('First value'); replaySubject.next('Second value'); replaySubject.subscribe(value => console.log(value));

BehaviorSubjects always emit the latest value to new subscribers, while ReplaySubjects can replay a specified number of previous values to new subscribers.

Example:

const behaviorSubject = new BehaviorSubject('Initial value'); behaviorSubject.next('Updated value'); behaviorSubject.subscribe(value => console.log(value));

'debounce' is used to discard values emitted by an Observable that follow each other too quickly, allowing only the last value within a specified time window to be emitted.

Example:

const debouncedObservable = inputObservable.pipe(debounce(() => timer(300)));