How do union types help with API response states?
PICTURE THIS: HOW TO EXPLAIN IT
Simple meaning
I model idle, loading, success with data, and error with a message as a discriminated union.
WHY — TypeScript instead of guessing?
Why interviewers care about TypeScript:
question about TypeScript.
trade-offs, and what you would actually do on a Frontend project - not buzzwords.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1I model idle, loading,
success with data, and error with a message as a discriminated union.
- 2Then the UI cannot
legally read data while status is loading.
- 3That is safer than
optional fields on one big object.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
I model idle, loading, success with data, and error with a message as a discriminated union. Then the UI cannot legally read data while status is loading.