TypeScript · Tier H

The 12 coding-interview patterns in TypeScript.

TL;DR

TypeScript is increasingly accepted in frontend-heavy interviews. Types articulate your data structures early — the interviewer sees your reasoning before you write the body.

TypeScript strengths

  • Discriminated unions clean up graph/tree traversal with node variants.
  • Generics on heap / trie / linked-list implementations read closer to pseudocode than JS.
  • The type checker catches off-by-one and nullability bugs mid-keystroke.

Watch-outs

  • Same JS heap gotcha — no built-in priority queue.
  • Wrestling the type checker on recursive types (`T extends T[]`) can eat your 45 minutes.
  • Some online IDEs don't compile TS — confirm before you start.

Reference idiom

type Node = { id: number; next: Node | null };
function toArray(head: Node | null): number[] {
  const out: number[] = [];
  for (let n = head; n !== null; n = n.next) out.push(n.id);
  return out;
}

Signature patterns in TypeScript

Graph BFS / DFSBreadth-first for shortest unweighted paths; depth-first for exhaustive traversal.Dynamic ProgrammingBreak an overlapping-subproblem problem into a recurrence and cache results.Sliding WindowMaintain a contiguous range and slide its boundaries to avoid recomputation.Two PointersTwo cursors moving independently over a sorted or monotone structure.

Frequently asked questions

Is TypeScript a good interview language?
TypeScript is increasingly accepted in frontend-heavy interviews. Types articulate your data structures early — the interviewer sees your reasoning before you write the body.
What TypeScript patterns come up most in coding interviews?
The signature patterns in TypeScript interviews: Graph BFS / DFS, Dynamic Programming, Sliding Window, Two Pointers.
What are common TypeScript interview pitfalls?
Same JS heap gotcha — no built-in priority queue. Wrestling the type checker on recursive types (`T extends T[]`) can eat your 45 minutes. Some online IDEs don't compile TS — confirm before you start.
Can I switch from Python to TypeScript mid-loop?
Most companies let you pick any language you're fluent in. Switching mid-loop usually hurts — pick the language you're fastest in and stick with it unless the company mandates otherwise.

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