tiny-deep-merge

A utility to deeply merge multiple plain objects.
Arrays are overwritten (not concatenated).
No options, no magic — deterministic merges.

🚀 Why use this?

• Deep merge of nested plain objects
• Merges any number of inputs
• Arrays and primitives are overwritten by default
• Zero dependencies (404 B minified and gzipped, compared to 723 B for deepmerge)
• Fully type-safe (TypeScript inference preserved)
• Does not mutate source objects

📦 Installation

npm install tiny-deep-merge
# or
pnpm add tiny-deep-merge
# or
yarn add tiny-deep-merge

🧪 Usage

// ES Module
import { merge } from "tiny-deep-merge"

// CommonJS
const { merge } = require("tiny-deep-merge")

const a = { user: { name: "Jess", age: 25 } }
const b = { user: { age: 31, active: true } }

const result = merge(a, b)
// => { user: { name: "Jess", age: 31, active: true } }

✅ Multi-object merge

merge({ a: 1 }, { b: 2 }, { c: { nested: true } })
// => { a: 1, b: 2, c: { nested: true } }

🧹 Arrays are overwritten by default

merge({ tags: ["a", "b"] }, { tags: ["c"] })
// => { tags: ["c"] }

🔒 Does not mutate source objects

const a = { count: 1 }
const b = { count: 2 }

const result = merge(a, b)

console.log(a) // { count: 1 }
console.log(result) // { count: 2 }

🧠 Type Safety

const merged = merge({ id: 1 }, { name: "Alice" }, { profile: { age: 25 } })

// merged: { id: number, name: string, profile: { age: number } }

🤨 What this does not do

• No array concatenation — arrays are overwritten.
• No merging of class instances, Maps, Sets, or Dates.
• No custom merge strategies.
• No runtime bloat.

📄 License

MIT @ John James