What are action creators and why do we use them?

An action creator is a function that creates and returns an action object. We typically use these so we don't have to write the action object every time we need it:

Here is an example of action creator:

Difficulty: 5/10

Topics: action creators, redux, async actions

Scenario Questions

0-2 years experience

1
How would you write an action creator that adds a new todo item to the Redux store?
2
If you dispatch an action creator that returns an object with a typo in the type field, what will the reducer see?
3
What fields must the object returned by an action creator contain for Redux to process it?

2-5 years experience

1
We need to submit a form, call an API, and store the result. How would you structure the action creators, and why might a plain object action creator be insufficient?
2
During a review you notice several action creators directly calling fetch, causing duplicated logic. How would you refactor them for better testability?
3
After adding a new action creator, the UI stopped updating. What steps would you take to debug the problem?

5-8 years experience

1
Our app has hundreds of action creators and bundle size is growing. What strategies would you use to reduce their impact at scale?
2
Describe how you would build a type‑safe action creator system in a TypeScript codebase, focusing on maintainability and IDE support.
3
If we need to log every dispatched action for analytics without touching each creator, how would you implement that efficiently?

8+ years experience

1
We are migrating a legacy codebase that uses stringly‑typed action creators to Redux Toolkit slices. What migration plan would you propose to minimize risk?
2
Multiple teams disagree on keeping action creators as separate functions versus inlining action objects in components. How would you evaluate the trade‑offs and set a guideline?
3
Design a shared library for action creators that supports both sync and async flows while allowing teams to extend it without breaking existing contracts.

Follow-up Questions

❓Can you walk me through what happens after you dispatch an action creator?
❓What are the trade‑offs between returning a plain object versus a thunk?
❓How would you unit‑test an action creator in isolation?