tiny-deep-merge

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

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🚀 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

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📦 Installation

1npm install tiny-deep-merge
2# or
3pnpm add tiny-deep-merge
4# or
5yarn add tiny-deep-merge

🧪 Usage

1// ES Module
2import { merge } from "tiny-deep-merge"
3
4// CommonJS
5const { merge } = require("tiny-deep-merge")
6
7const a = { user: { name: "Jess", age: 25 } }
8const b = { user: { age: 31, active: true } }
9
10const result = merge(a, b)
11// => { user: { name: "Jess", age: 31, active: true } }

✅ Multi-object merge

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

🧹 Arrays are overwritten by default

1merge({ tags: ["a", "b"] }, { tags: ["c"] })
2// => { tags: ["c"] }

🔒 Does not mutate source objects

1const a = { count: 1 }
2const b = { count: 2 }
3
4const result = merge(a, b)
5
6console.log(a) // { count: 1 }
7console.log(result) // { count: 2 }

🧠 Type Safety

1const merged = merge({ id: 1 }, { name: "Alice" }, { profile: { age: 25 } })
2
3// 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.

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📄 License

MIT @ John James