Filter instanceof type

[SergeyDvornikov]

I am not the first nor the last to run into type guard issues when using the filter operator with instanceof (especially in strict mode).
A very strong example:

router.events
  .pipe(
    filter(e => e instanceof NavigationEnd),
    map(e => e.urlAfterRedirects),
    // TS2339: Property 'urlAfterRedirects' does not exist on type 'Event'. 
    // Property 'urlAfterRedirects' does not exist on type 'RouterEvent'.
   ...
  )
  .subscribe();

One solution is to use an explicit type cast. For example:

router.events
  .pipe(
    filter(e => e instanceof NavigationEnd),
    map(e => e as NavigationEnd),
    map(e => e.urlAfterRedirects),
   ...
  )
  .subscribe();

I also came across other suggestions and methods here:
#4947
#3473
https://gist.github.com/jayoungers/63bf0bce77d28e448a41f5bb4c531264

None of these discussions of suggestions or ways are (to me) simple and elegant, and I decided to try to go the other way. You can use the method (function)-factory, which would take the class parameter to which you want to apply instanceof and return the type guard function:

function instanceOf<T, S extends T>(type: new (...args: any[]) => S): (value: T) => value is S {
  return function(value: T): value is S {
    return value instanceof type;
  };
}

A check was made in strict mode:

    this.router.events
      .pipe(
        takeUntil(this.ngUnsubscribe),
        filter(instanceOf(NavigationEnd))
      )
      .subscribe(e => console.warn(e.urlAfterRedirects));

No issues found.
I also think, if necessary, you can try to expand the functionality to accept several classes in the factory