Technologies Coding Problems Bookmarks Learning Paths

Technologies Coding Problems Bookmarks Learning Paths

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Questions

8 of 8

1What is TypeScript?

2What is 'type inference' in TypeScript?

3How does typescript help in writing better code

4Discuss unknown type compare it with any type.

5What is duck/structural typing?

6What is contextual typing?

7How does TypeScript handle strict null checks?

8What is downleveling?

typescript

Commands and Packages

08 / 08

What is downleveling? | Basics | typescript Interview Questions | NextRound.in

What is downleveling?

Difficulty: 5/10

target, compiler options, compatibility

Downleveling is the process of TypeScript compiling modern JavaScript syntax down to an older version of JavaScript so it can run in environments that don't support newer features.

Scenario Questions

0-2 years experience

1We need a new component that must run in IE11. How would you set up tsconfig so the emitted JavaScript is compatible?
2If you add optional chaining to a file that’s compiled for ES5, what will the output look like and why?

2-5 years experience

1Our TypeScript library is published with a target of ES2020, but some consumers on Node 10 are seeing syntax errors. Walk me through how you’d debug and fix the downleveling issue.
2Explain why a piece of code using async/await throws at runtime after compilation to ES5, and what steps you’d take to resolve it.

5-8 years experience

1In a monorepo, some packages need to downlevel to ES5 for a legacy web app while others can stay at ES2022. How would you design the build pipeline to handle these mixed targets efficiently?
2Discuss the trade‑offs between downleveling async/await to generator helpers versus pulling in a runtime polyfill for a large single‑page application.

8+ years experience

1We’re planning a multi‑year migration from an ES5 front‑end to a modern ES2022 stack. What architectural guidelines would you establish for downleveling strategy, versioning, and CI/CD to keep backward compatibility while gradually retiring polyfills across teams?
2How would you coordinate cross‑team decisions about downleveling targets to avoid version drift in a large organization with both legacy and cutting‑edge products?

Follow-up Questions

What problems can arise if you target a version that's too low for your codebase?
How does downleveling interact with source‑map generation and debugging?
When might you choose to avoid downleveling altogether?

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