mergeMap vs concatMap vs exhaustMap in Angular - When to Use Which

The Big Idea

Discover how these three operators can save your app from chaos when handling many tasks at once!

The Scenario

Imagine you have multiple tasks that start one after another, like sending several requests to a server when a user clicks buttons quickly.

You try to handle each request manually, starting a new one every time without waiting for the previous to finish.

The Problem

Manually managing these overlapping tasks is confusing and error-prone.

You might send too many requests at once, causing overload or unexpected results.

Or you might accidentally ignore some tasks or run them in the wrong order.

The Solution

Using mergeMap, concatMap, and exhaustMap operators in Angular helps control how tasks run and overlap.

They let you decide if tasks run all at once, one after another, or ignore new tasks while busy.

This makes your code simpler, safer, and easier to understand.

Before vs After

✗ Before

buttonClicks.forEach(() => { sendRequest(); });

✓ After

buttonClicks.pipe(mergeMap(() => sendRequest()));

What It Enables

They enable smooth, predictable handling of multiple asynchronous tasks, improving app performance and user experience.

Real Life Example

When a user clicks a search button multiple times quickly, concatMap queues the requests so they run one by one, avoiding server overload.

Key Takeaways

mergeMap runs all tasks simultaneously.

concatMap runs tasks one after another, preserving order.

exhaustMap ignores new tasks while one is running.