Provyn Prep · JavaScript and TypeScript competency
Async & type safety in the JavaScript and TypeScript assessment
Async & type safety is one of the areas a Provyn JavaScript and TypeScript credential scores separately, so a recruiter can see it on its own rather than averaged into one number. This guide explains what it covers, how it is tested and what to practice.
What it covers
Promises, async/await and the event loop, plus using TypeScript's type system to make code safer.
Topics in the practice set for this area
- async
- TypeScript typing
How it is tested
In the timed assessment, questions in this area use these formats: code you write, fill-in-the-blank code, multiple choice, put the steps in order. Each attempt draws its own set of questions, and this area gets its own sub-score on the credential when the attempt includes enough questions from it. The assessment questions themselves are never published; the practice set below is written separately for study.
What to practice
- Order the console output of a snippet mixing setTimeout, promise callbacks and synchronous logs before running it.
- Convert callback code to async/await with correct error handling.
- Type a function with generics and a union return type, then narrow the union at the call site.
Try a practice question
From the free practice set (6 questions in this area). Answers and explanations are in the practice set.
- `Promise.all([p1, p2])` rejects when:
- TypeScript's `unknown` differs from `any` because:
- A TypeScript interface vs. a type alias — which can NOT be merged across declarations?
Practice before the real thing
Both are free and use practice questions only, never questions from the real assessment.
More JavaScript and TypeScript study guides
Last reviewed 2026-10-06.