High TypeScript Question 153 of 229

How do you type a discriminated union for UI state?

Frontend Master · Speak this in 60–90 seconds · Faridabad & Delhi NCR

PICTURE THIS: HOW TO EXPLAIN IT

IdeaTypeScript

HowWhat happens inside

Why they askShows real use

Simple meaning

I use a status field like idle, loading, success, error and narrow with a switch.

WHY — TypeScript instead of guessing?

Why interviewers care about TypeScript:

This is a process

question about TypeScript.

Panels listen for order,

trade-offs, and what you would actually do on a Frontend project - not buzzwords.

Stay structured

Name the idea, why it exists, then one short example.

Close cleanly

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:

1
I use a status
field like idle, loading, success, error and narrow with a switch.
2
Success carries data, error
carries a message, loading carries none.
3
That makes impossible states
unrepresentable, which is what Amazon-style interviews want to hear.
4
Give an example
One tiny concrete case you can say aloud.
5
Common mistake
What juniors usually get wrong.
6
Close
When you pick this over the alternative.

EXAMPLE — See it in action

Here's a short line you can speak, broken into clear beats:

Say this line

“Success carries data, error carries a message, loading carries none.”

Break into beats

Successcarriesdataerrorcarriesa

Speaking order

2987408337471632900

Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.

Key takeaway

I use a status field like idle, loading, success, error and narrow with a switch. Success carries data, error carries a message, loading carries none.