Object Diff

Typed deep comparison, change records, and JSON Patch generation for structured snapshots.

Install

npm install @jayoncode/object-diff

pnpm add @jayoncode/object-diff

yarn add @jayoncode/object-diff

Example: detect changes and apply a patch

import { diff, hasChanges, patch, applyPatch } from "@jayoncode/object-diff";

const before = { user: { name: "John", role: "viewer" }, active: true };
const after = { user: { name: "Jane", role: "admin" }, active: true };

if (hasChanges(before, after)) {
  const result = diff(before, after);
  const operations = patch(result);
  const synced = applyPatch(before, operations);
  // synced matches `after` for tracked paths
}

Use diff() for audit trails and inspectors; hasChanges() for dirty checks; patch() / applyPatch() to propagate updates between stores or clients.

Inspect changes interactively →

Problem → approach

Typical pain	Object Diff
JSON.stringify(a) !== JSON.stringify(b) — no paths, no types, order-sensitive	diff() returns typed change records with paths (user.name, items[2])
Hand-rolled deep equality and patch logic for optimistic UI	patch() / applyPatch() emit and apply RFC 6902 operations
Explaining what changed in PRs or logs requires custom formatting	serialize() exports JSON, Markdown, or table views from the same diff

Overview

Object Diff compares plain objects and arrays, emits structured change records, and can serialize results or produce RFC 6902-style patch operations.

API	Purpose
diff(a, b)	Full change list with paths and types
hasChanges(a, b)	Boolean dirty check without full diff cost
patch(diffResult)	Generate patch operations
applyPatch(target, ops)	Immutable apply
serialize(diff, format)	JSON, Markdown, or table export

Documentation path

Foundation

#	Guide	Topics	Playground
1	Tutorial	Install, first diff	Dashboard
2	Core concepts	Snapshots, changes, patches	Diff

Core APIs

#	Guide	Topics	Playground
3	Diffing	Options, filtering, helpers	Diff
4	Patching	Apply, revert, edge cases	Patch

Output and performance

#	Guide	Topics	Playground
5	Serialization	Export formats	JSON
6	Performance	Large-object benchmarks	Benchmarks

Package fit

Requirement	API
Form/state dirty detection	hasChanges(a, b)
Structured audit log	diff() change records
Partial sync between clients	patch() + applyPatch()
Human-readable changelogs	serialize(..., "markdown")

Reference

• API (TypeDoc)
• Playground guide
• Examples