managing-state-defer.ts

import { defer, MonoTypeOperatorFunction } from "rxjs";
import { tap } from "rxjs/operators";

export function debug<T>(): MonoTypeOperatorFunction<T> {
  return source => defer(() => {
    let index = -1;
    return source.pipe(
      tap(t => console.log(`[${++index}]: ${t}`))
    );
  });
}