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Data Helper 2: Set Value by Path

By FrontendAtlas Team · Updated Jan 30, 2026

Implement setByPath(obj, path, value) that returns a new object/array tree with the value written at the nested path. Normalize dot or segment paths, create missing containers based on numeric segments, and never mutate the original input. Empty paths should return the value directly, and primitives…

What you’ll build / What this tests

This premium javascript coding focuses on Data Helper 2: Set Value by Path. You’ll apply objects and arrays thinking with intermediate level constraints. The prompt emphasizes Implement setByPath(obj, path, value) that returns a new object/array tree with the value written at the….

Learning goals

Translate the prompt into a clear javascript API signature and return shape.
Apply objects, arrays, immutability techniques to implement data helper 2: set value by path.
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.
Choose iteration vs higher-order methods for readability.
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

Preserve input order and handle empty arrays safely.
Avoid prototype pitfalls when reading object keys.
Avoid deep recursion issues on large inputs.
Do not mutate input arrays; preserve item order.
Avoid mutating nested objects; return new references.
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 obj = /* data helper 2: set value by path input */;
const path = /* config */;
const result = setByPath(obj, path);
console.log(result);

// Edge case check
const empty = obj && path ?? null;
const fallback = setByPath(obj, path);
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.