Node.js Modules Interview Questions With Answers
Modules come up in Node.js interviews. Here are the common questions and how to answer them.
Node.js Modules Interview Questions With Answers
Modules come up in every Node.js interview. Here are the common questions and how to answer them.
What is the difference between module.exports and exports?
exports is a reference to module.exports initially. You can add properties to exports (exports.add = fn) or reassign module.exports (module.exports = fn). Mixing both breaks the link, causing bugs.
How does require work?
require reads a file, runs it once, caches the result, and returns the file's module.exports. Subsequent requires return the cached object without re-running the file.
What is module caching and why does it matter?
Modules run once and are cached. This enables singletons for shared state like database connections, but means requiring the same file twice returns the same object. Export a factory function for fresh state.
What is the difference between CommonJS and ES modules?
CommonJS uses require and module.exports, is synchronous, and loaded at runtime. ES modules use import and export, are async, and statically analyzable. Pick one per project.
What are circular dependencies and how do you handle them?
When A requires B and B requires A. Node.js returns a partially loaded module, which can cause bugs. Avoid by restructuring so dependencies go one way, or use lazy require inside functions.
The Takeaway
Know module.exports vs exports, how require works, module caching, CommonJS vs ES modules, and circular dependencies. These are the core module interview questions for Node.js.
exports is a reference to module.exports initially. You can add properties to exports or reassign module.exports. Mixing both breaks the link, since reassigning module.exports makes exports point to the old object. Pick one approach per file.
require reads a file, runs it once, caches the result, and returns the file's module.exports. Subsequent requires return the cached object without re-running the file, so a module's code runs once.
Modules run once and are cached after first require. This enables singletons for shared state like database connections, but means requiring the same file twice returns the same object. Export a factory function for fresh state on each use.
CommonJS uses require and module.exports, is synchronous, and loaded at runtime. ES modules use import and export, are async, and statically analyzable. Pick one per project to avoid mixing issues.
When A requires B and B requires A. Node.js returns a partially loaded module, which can cause bugs. Avoid by restructuring so dependencies go one way, or use lazy require inside functions so the require happens when the function runs, not on load.
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