hardLow-Level Design

How do you handle circular dependencies in Node.js?

Q: How do you handle circular dependencies in Node.js?

**TL;DR.** A **circular dependency** is when module A requires B and B requires A. Node won't infinite-loop — it returns a **partial export** of whichever module is still mid-execution. That can yield undefined imports if you use them at load time. Fix by **restructuring** (extract shared code into a third module), deferring access, or using late require . module A module B require(B) <path class='d-edge-dashed' d='M288 90 H172' marker

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Tests structural coding knowledge and understanding of how CommonJS loads modules.

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Why the import is undefined — and the fix

// a.js
const b = require('./b');
console.log('b.value at load:', b.value);  // undefined (b not finished)
module.exports.fromA = 'A';

// b.js
const a = require('./a');                  // a is mid-load → partial
module.exports.value = 42;
// Fix: read a.fromA inside a function, not at top level.

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