Question 1

Compare CommonJS (CJS) and ES Modules (ESM) in Node.js. How does the runtime handle them?

Accepted Answer

CJS is synchronous and uses require() at runtime, while ESM uses static import/export and resolves the dependency graph asynchronously before execution.

Question 2

What is the 'exports' field in package.json, and how does it improve on the older 'main' field?

Accepted Answer

It lets you define a package's official entry points, control access to internal files, and select different outputs for CJS and ESM.

Question 3

How does Node.js handle circular dependencies between CJS and ESM?

Accepted Answer

CJS returns an incomplete exports object while modules load synchronously, whereas ESM links live bindings, but reading an uninitialized variable can throw a ReferenceError.

Question 4

What is the difference between npm install and npm ci, and why is package-lock.json important?

Accepted Answer

npm ci removes node_modules and installs the exact versions specified in package-lock.json for a reproducible build, while npm install may update packages within their SemVer ranges.

Question 5

How do npm/pnpm Workspaces manage monorepos, and what are their benefits?

Accepted Answer

They let you manage multiple packages in one repository, share dependencies, and link local packages to each other as symlinks without publishing them.

Question 6

What is the Dual Package Hazard when publishing a library that supports both CJS and ESM in Node.js?

Accepted Answer

It occurs when the same application imports two different instances of a library, duplicating singletons and breaking instanceof checks.

Question 7

How do you use Node.js's built-in test runner (node:test) without external libraries?

Accepted Answer

The node:test module and node:assert provide a fast, built-in test environment with test, describe, and it functions.

Question 8

What do the ^ and ~ symbols mean in package.json, and how do they differ from an exact version?

Accepted Answer

^ permits compatible Minor and Patch updates, while ~ limits updates to Patch versions; omitting a symbol pins the exact version.

Question 9

Why is the node: prefix useful when importing built-in modules such as node:fs and node:path?

Accepted Answer

It clearly identifies a module as built in, prevents dependency confusion, and speeds up module resolution.

Question 10

How does modern Node.js support running TypeScript files directly with Type Stripping?

Accepted Answer

Type Stripping is enabled by default starting in Node.js 22.18 and 23.6, so you can run a TypeScript file directly with node app.ts without build tools; older versions require the --experimental-strip-types flag.