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Find the Corresponding Node in Twin DOM Trees

By FrontendAtlas Team · Updated Feb 1, 2026

Given two identical DOM trees and a node in tree A, return the corresponding node in tree B. Traverse both trees in sync or compute a path index. Complexity: O(n) time, O(h) stack.

What you’ll build / What this tests

This premium javascript coding focuses on Find the Corresponding Node in Twin DOM Trees. You’ll apply dom and tree thinking with intermediate level constraints. The prompt emphasizes Given two identical DOM trees and a node in tree A, return the corresponding node in….

Learning goals

Translate the prompt into a clear javascript API signature and return shape.
Apply dom, tree, traversal techniques to implement find the corresponding node in twin dom trees.
Handle intermediate edge cases without sacrificing readability.
Reason about time/space complexity and trade-offs in javascript.

Key decisions to discuss

Define the exact input/output contract before coding.
Prioritize predictable edge-case handling over micro-optimizations.

Evaluation rubric

Correctness: covers required behaviors and edge cases.
Clarity: readable structure and predictable control flow.
Complexity: avoids unnecessary work for large inputs.
API discipline: no mutation of inputs; returns expected shape.
Testability: solution is easy to unit test.

Constraints / Requirements

Avoid deep recursion issues on large inputs.
Do not access the real DOM; use the provided node shape.
Handle empty or missing inputs without throwing errors.
Keep runtime close to linear time where possible.
Prefer a pure function: no side effects beyond the return value.

Mini snippet (usage only)

// Example usage
const rootA = /* find the corresponding node in twin dom trees input */;
const rootB = /* config */;
const result = findTwin(rootA, rootB);
console.log(result);

// Edge case check
const empty = rootA && rootB ?? null;
const fallback = findTwin(rootA, rootB);
console.log(fallback);

// Expected: describe output shape, not the implementation
// (no solution code in preview)

Common pitfalls

Mutating inputs instead of returning a new value.
Skipping edge cases like empty input, duplicates, or nulls.
Overlooking time complexity for large inputs.