Alert: User is currently engaging in typing activity, utilizing a streamlined RXJS approach

Question

Alert: User is currently engaging in typing activity, utilizing a streamlined RXJS approach

In my current project, I am in the process of adding a feature that shows when a user is typing in a multi-user chat room. Despite my limited understanding of RXJS, I managed to come up with the code snippet below which satisfies the basic requirements for the "User is Typing" feature:

   this.messageForm.message.valueChanges
      .pipe(
        tap(() => this.convoService.isUserTyping(true)),
        debounceTime(500),
        map(() => this.convoService.isUserTyping(false))
      )
      .subscribe();

However, this implementation is not efficient as it sends too many requests to the server. My objective is to restrict requests to only 2, and utilize RXJS operators to achieve the following specific behaviors:

Send a request on the initial keypress
Disregard any subsequent keypresses
Wait for a set duration after the last keypress
Restart the timer if a new keypress occurs before the timer ends
Send a request once the timer expires

angular typescript rxjs6

Answer 1

Answer №1

Here is a method that ensures no side effects:

const userInput$ = this.messageForm.message.valueChanges.pipe(
  switchMap(() => concat(
    of(true),
    of(false).pipe(delay(500)),
  )),
  distinctUntilChanged(),
)

You can utilize this to handle your requests. If isUserTyping is a fire-and-forget task, you can simply use

userInput$.subscribe(typing => this.convoService.isUserTyping(typing));

If it involves an asynchronous operation (and returns an observable) I would suggest the following approach:

userInput$.pipe(
  concatMap(typing => this.convoService.isUserTyping(typing))
).subscribe();

This method ensures that all requests are executed in sequence, preventing any out-of-order issues especially in high-latency scenarios¹.

¹ If latency becomes a significant concern, additional measures such as buffering may be needed to prevent excessive backpressure on the requests. However, for the scope of this question, that level of detail is unnecessary.

Answer 2

Here is a method that ensures no side effects:

const userInput$ = this.messageForm.message.valueChanges.pipe(
  switchMap(() => concat(
    of(true),
    of(false).pipe(delay(500)),
  )),
  distinctUntilChanged(),
)

You can utilize this to handle your requests. If isUserTyping is a fire-and-forget task, you can simply use

userInput$.subscribe(typing => this.convoService.isUserTyping(typing));

If it involves an asynchronous operation (and returns an observable) I would suggest the following approach:

userInput$.pipe(
  concatMap(typing => this.convoService.isUserTyping(typing))
).subscribe();

This method ensures that all requests are executed in sequence, preventing any out-of-order issues especially in high-latency scenarios¹.

¹ If latency becomes a significant concern, additional measures such as buffering may be needed to prevent excessive backpressure on the requests. However, for the scope of this question, that level of detail is unnecessary.

Alert: User is currently engaging in typing activity, utilizing a streamlined RXJS approach

Answer №1

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