---
title: 🟠 High Order Operator Bug
description: Challenge 11 is about resolving a Rxjs bug because of high order operators
author: Thomas Laforge
challengeNumber: 11
command: rxjs-pipe-bu
sidebar:
  order: 114
---

:::note
WIP: The following documentation will be reviewed and improved. However, you can still take on the challenge. If you don't understand a certain part, please feel free to reach out or create an issue.
:::

Let's dive inside the wonderful word of RxJs.

This challenge is inspired by a real-life example.

## Presentation of the challenge

### User Story

We need a button for each `Topic`. When we click on it, we delete all objects with this `Topic` in our database _(Fake DB in our case)_. Finally we display **All [topic] have been deleted** is everything was deleted successfully or **Error: deletion of some [topic] failed** if some deletions failed

### Constraints:

We can only pass one object to our DB for deletion at the time. The DB will respond true if the data was successfully deleted and false otherwise.

### What you need to do

The QA team reports a **bug**. The UI shows **All [topic] have been deleted** all the time, even if some deletions fail.

👉 Spot the bug and correct it.
