Node.JS isDeepStrictEqual

Chat GPT 4o answer

Here’s a quick evaluation based on your context:

✅

util.isDeepStrictEqual(lhs, rhs)

Pros

• Deep comparison of objects, arrays, nested structures, etc.

• Strict equality: compares values using === semantics where applicable.

• Native: no need to install extra dependencies (like lodash).

• Safe: handles edge cases like cyclical structures.

• Stable: as of Node.js v9+, and still supported.

⚠️ Considerations

• Performance: For large nested objects, it’s slower than shallow comparison.

• Node.js-only: not available in browser environments.

• No customization: You can’t define how properties should be compared (e.g., by key transformation or ignoring some fields).

In Your Case (e.g., VO.equals)

Since your DayAvailability#equals() is already tailored (e.g., handling only first 144 bits of Uint32Array, ignoring unused bits, comparing a Map<number, string>), isDeepStrictEqual would not be a suitable drop-in replacement.

However, for comparing plain objects like:

const a = { h: 0, m: 10 };
const b = { h: 0, m: 10 };

import { isDeepStrictEqual } from 'node:util';
console.log(isDeepStrictEqual(a, b)); // ✅ true

…it works perfectly.

✅ When to use

isDeepStrictEqual

• Unit tests that compare DTOs, POJOs, or JSON-like structures

• Deep nested data like { user: { profile: { name: 'Alice' } } }

• Comparing object snapshots (like Jest snapshot tests)

❌ When not to use

• Performance-sensitive hot paths

• Comparing custom Value Objects with special comparison rules (like DayAvailability)

• Cross-platform (browser/Node) shared code

🔧 Alternative for browser

If you’re working in a shared environment (browser + Node), consider:

npm install fast-deep-equal

import deepEqual from 'fast-deep-equal';

deepEqual(a, b);

Let me know if you want to benchmark isDeepStrictEqual or wrap it for optional shallow/deep toggles.