Question 1

How does Node resolve require('pkg')?

Accepted Answer

Looks at node_modules hierarchy, package.json main/exports, and core modules — algorithm is hierarchical. Understanding exports maps and conditional exports prevents dual-package hazards. Core modules take precedence by name.

Question 2

What is the dual package hazard?

Accepted Answer

Shipping both CJS and ESM that evaluate twice, breaking singleton identity (two copies of a module). Careful package.json exports and documentation matter. Consumers importing differently can get two React/Nest instances — subtle bugs.

Question 3

ESM top-level await — implications?

Accepted Answer

Modules can await at top level, delaying dependents until resolution. Useful for dynamic config; can complicate circular deps and startup time. Use deliberately.

Question 4

How do circular dependencies behave in CJS vs ESM?

Accepted Answer

CJS may get partial exports; ESM live bindings can still be in TDZ — both can surprise. Refactor to break cycles: extract shared types/utils, invert dependencies. Cycles are a design smell in large apps.

Question 5

When do you use dynamic import()?

Accepted Answer

Code-splitting, optional/heavy deps, and conditional loading after feature flags. Returns a promise. Works in CJS and ESM. Useful for reducing startup cost of CLIs and servers.

Question 6

Lead: monorepo package strategy for Node services?

Accepted Answer

Clear public exports, workspace protocol, shared lint/tsconfig, and versioning policy for published packages. Avoid deep relative imports across apps. Enforce dependency direction. CI builds affected packages only.

Modules Node.js Interview Questions

Other Node.js interview topics