Deep Object Comparison in JavaScript: deep-diff vs deep-object-diff vs object-diff

When building frontend applications that track state changes — like form validation, real-time sync, or undo stacks — you often need to compare complex nested objects. Native equality checks (===) fail here because they only compare references. That’s where dedicated diffing libraries come in. Let’s examine how deep-diff, deep-object-diff, and object-diff approach this problem, and why one might be better suited for your use case.

⚠️ Deprecation Status: Don’t Use object-diff

First, a critical note: object-diff is deprecated. Its npm page states: "This package has been deprecated. Please use deep-object-diff instead." The GitHub repo is archived and read-only. It also has significant limitations:

• Only compares plain objects (ignores arrays, dates, regexes, etc.)
• No support for nested structures beyond one level
• Returns an empty object {} even when differences exist in deeper levels

// object-diff (deprecated — do not use)
import objectDiff from 'object-diff';

const a = { user: { name: 'Alice', age: 30 } };
const b = { user: { name: 'Alice', age: 31 } };

console.log(objectDiff(a, b)); // {} — fails to detect nested change!

Given these flaws and its unmaintained status, skip object-diff entirely. We’ll focus the rest of this comparison on the two viable options.

📦 Output Format: Structured Metadata vs Plain Delta

The biggest difference between deep-diff and deep-object-diff lies in what they return.

deep-diff gives you an array of change records, each describing the type of operation (N for new, D for deleted, E for edited, A for array), the path to the change, and old/new values.

// deep-diff
import diff from 'deep-diff';

const a = { user: { name: 'Alice', tags: ['dev'] } };
const b = { user: { name: 'Bob', tags: ['dev', 'frontend'] } };

const changes = diff(a, b);
console.log(changes);
// [
//   { kind: 'E', path: ['user', 'name'], lhs: 'Alice', rhs: 'Bob' },
//   { kind: 'A', path: ['user', 'tags'], index: 1, item: { kind: 'N', rhs: 'frontend' } }
// ]

This format is powerful when you need to interpret or replay changes — for example, to generate audit logs or apply patches later.

deep-object-diff, by contrast, returns a plain object showing only the paths and new values that differ. Deleted keys are represented with undefined.

// deep-object-diff
import diff from 'deep-object-diff';

const a = { user: { name: 'Alice', tags: ['dev'] } };
const b = { user: { name: 'Bob', tags: ['dev', 'frontend'] } };

const delta = diff(a, b);
console.log(delta);
// { user: { name: 'Bob', tags: ['dev', 'frontend'] } }

// For deletions:
const c = { name: 'Alice', role: 'admin' };
const d = { name: 'Alice' };
console.log(diff(c, d)); // { role: undefined }

This is simpler and integrates cleanly with patterns like Object.assign() or spread operators, making it great for lightweight state updates.

🔁 Applying Patches: Built-in vs Manual

If you need to apply a diff back to an object (e.g., to revert a change), deep-diff includes a patch function:

// deep-diff: applying patches
import { diff, patch } from 'deep-diff';

const original = { count: 5 };
const updated = { count: 10 };
const changes = diff(original, updated);

const reverted = patch(updated, changes.map(change => ({
  ...change,
  kind: change.kind === 'E' ? 'E' : change.kind, // invert logic as needed
  // Note: full inversion requires custom logic per kind
})));
// deep-diff doesn't auto-invert, but provides tools to build patching

deep-object-diff has no built-in patching. You’d merge the delta manually:

// deep-object-diff: manual merge
import diff from 'deep-object-diff';

const base = { a: 1, b: 2 };
const delta = diff(base, { a: 3 });

const merged = { ...base, ...delta }; // { a: 3, b: 2 }
// But this fails for nested deletes — you'd need a recursive merge utility

So if patching or undo functionality is core to your app, deep-diff’s structured output gives you more control.

🧪 Handling Edge Cases: Arrays, Dates, and Circular References

Both libraries handle nested objects and arrays, but differently.

Arrays:

• deep-diff treats array modifications as special A (array) kind entries, showing index-level changes.
• deep-object-diff returns the entire new array if any element differs.

// Array handling
const arrA = { items: [1, 2] };
const arrB = { items: [1, 3] };

// deep-diff
console.log(diff(arrA, arrB));
// [{ kind: 'A', path: ['items'], index: 1, item: { kind: 'E', lhs: 2, rhs: 3 } }]

// deep-object-diff
console.log(diff(arrA, arrB));
// { items: [1, 3] }

Dates and other objects:

• deep-diff compares Date objects by value (via .getTime()), and handles RegExp, Buffer, etc.
• deep-object-diff compares non-plain objects by reference, so two new Date('2023') instances will appear different even if they represent the same time.

Circular references:

• deep-diff detects and safely skips circular structures.
• deep-object-diff may crash or recurse infinitely on circular objects (though recent versions attempt basic cycle detection).

🛠️ API Simplicity and Functional Style

deep-object-diff follows a pure functional style: one function, one job, no side effects.

import diff from 'deep-object-diff';
const delta = diff(obj1, obj2);

deep-diff offers more methods (diff, patch, applyChange, revertChange) and optional configuration (like prefiltering properties), which adds flexibility at the cost of API surface area.

🌐 Real-World Use Cases

Case 1: Redux State Change Detection

You want to avoid unnecessary re-renders by checking if state actually changed.

• ✅ Best choice: deep-object-diff
• Why? You only care whether the result is {} (no change) or not. Simple and fast.

const prev = store.getState();
const next = reducer(prev, action);
if (Object.keys(diff(prev, next)).length > 0) {
  // dispatch update
}

Case 2: Audit Logging in Admin Panel

You need to log exactly what changed in a user profile (e.g., “email changed from X to Y”).

• ✅ Best choice: deep-diff
• Why? The structured output lets you generate human-readable messages per field.

const changes = diff(oldProfile, newProfile);
changes.forEach(change => {
  if (change.kind === 'E') {
    console.log(`${change.path.join('.')} changed from ${change.lhs} to ${change.rhs}`);
  }
});

Case 3: Syncing Client State with Server

You send only changed fields to reduce payload size.

• ✅ Best choice: deep-object-diff
• Why? The delta object maps directly to a PATCH request body.

const local = { name: 'Alice', email: 'a@example.com' };
const server = { name: 'Alice', email: 'old@example.com' };

const patchBody = diff(server, local); // { email: 'a@example.com' }
fetch('/api/user', { method: 'PATCH', body: JSON.stringify(patchBody) });

📊 Summary Table

💡 Final Recommendation

• If you need detailed, actionable insights into how objects changed — and you’re okay with a slightly heavier API — go with deep-diff, but test thoroughly in your environment.
• If you want a lightweight, predictable delta for simple comparisons or state updates, deep-object-diff is the modern, reliable choice.
• Never use object-diff — it’s deprecated and fundamentally broken for real-world data.

In most contemporary frontend applications, deep-object-diff strikes the best balance between simplicity, correctness, and maintainability. Reserve deep-diff for specialized scenarios where its rich metadata justifies the added complexity.