Live coding
TypeScript Interview Copilot
TypeScript interviews add a second axis to every question: the solution has to work, and the types have to say something true about it.
The round
What a TypeScript interview actually looks like
Front-end and full-stack loops increasingly run their coding round in TypeScript rather than JavaScript, and the type layer is where the round gets interesting. Expect to be asked to type a function you just wrote, to explain why a union did not narrow, or to build a small generic utility. Some interviewers deliberately hand you code with `any` in it and ask what you would tighten.
What you get back
Solutions come back with real signatures rather than `any` escape hatches: generics where a function is genuinely polymorphic, discriminated unions where the shape varies by tag, and `unknown` with a narrowing step where input is untrusted. When the question is about the type system itself, the answer explains what the compiler infers and at which line, because that is the reasoning the interviewer is listening for.
Example prompts
Questions people are actually asked
Send the transcript straight to the coding surface, or snip the problem off the screen.
Type a function that takes a key of an object and returns its value.
Why does this union not narrow inside the callback?
Write a utility type that makes nested properties optional.
Where candidates lose points
TypeScript-specific traps
Casting instead of narrowing
An `as` assertion silences the compiler without proving anything. Interviewers read it as a candidate who has not internalised what the checker is for.
Interfaces versus type aliases
The real difference is declaration merging and how each behaves in a public API. Answering with a style preference misses what is being asked.
Forgetting types are erased
Runtime validation still has to exist. A candidate who types an API response and calls it validated has been caught by exactly the question that was set.
Three surfaces
One workspace, three kinds of round
Chat
Behavioral rounds and the “tell me about a time” half of a technical screen, in your own voice.
Live coding
A structured solution with the reasoning attached, so you can talk through the code while you write it.
System design
Architecture answers with the diagram rendered inline, not described in prose.
Choosing a model
Keep reading
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Dart Interview Copilot
Live help for Dart and Flutter interviews: futures and streams, sound null safety, and widget-lifecycle answers that hold up to follow-ups.
System design copilot
Architecture rounds with the diagram rendered inside the answer.
Platform setup: coderpad · hackerrank