rxjs-ajax-retry.js

// Credit: https://www.learnrxjs.io/operators/error_handling/retrywhen.html.

import { throwError, timer } from 'rxjs';
import { ajax } from 'rxjs/ajax';
import { finalize, mergeMap, retryWhen } from 'rxjs/operators';

const genericRetryStrategy = ({
  maxRetryAttempts = 3,
  scalingDuration = 5000
} = {}) => errors =>
  errors.pipe(
    mergeMap((error, index) => {
      const retryAttempt = index + 1;
      if (retryAttempt > maxRetryAttempts) {
        return throwError(error);
      }
      console.log(
        `Attempt ${retryAttempt}: Retrying in ${retryAttempt *
          scalingDuration}ms`
      );
      return timer(retryAttempt * scalingDuration);
    }),
    finalize(() => console.log('We are done!'))
  );

const req = ajax
  .getJSON('https://jsonplaceholder.typicode.com/todos/1')
  .pipe(retryWhen(genericRetryStrategy()));

req.subscribe({
  next(x) {
    console.log('next', x);
  },
  error(error) {
    console.error('error', error);
  },
  complete() {
    console.log('complete');
  }
});