Strongly-typed deep and recursive object merging with support for all value types.

Install

pnpm add object-deep-merge

yarn add object-deep-merge

npm install object-deep-merge

Basic Usage

import { merge } from "object-deep-merge";

Simply merge two objects, with no nested properties

const merged = merge({ foo: false }, { bar: true });

console.log({ merged });

Output

{
    "merged": {
        "foo": false,
        "bar": true
    }
}

Typed Usage

merge Type Signature

The merge function accepts two optional type generics. TData and TResult.

function merge<TData extends MergeableObject = MergeableObject, TResult extends MergeableObject = TData>(
    source: TData,
    target: TData,
    ...targets: Array<TData>
): TResult;

Important

The Merge and MergeDeep types from type-fest are shipped from this library as a convenience. It is not unreasonable to use those types directly instead.

Without explicitly passing in types the function will infer the shape of the object(s) passed in.

• Passing in TData will validate the shape of the objects passed in.
• Passing in TResult will override the output type. While this should be used sparingly, it provides a convenient approach for correctly typing partial types into complete types.

Simple Example w/o Generics

type Data = {
    name: string;
    description: string;
};

const base: Data = { name: "object-deep-merge", description: "merge objects" };

const overrides: Partial<Data> = { description: "merge objects, deeply" };

const merged = merge(base, overrides);

// Type is inferred so the signature becomes:
// function merge<Partial<Data>, Partial<Data>>(source: Partial<Data>, target: Partial<Data>, ...targets: Partial<Data>[]): Partial<Data>

// TData    = Partial<Data>
// TResult  = Data

console.log({ merged });

Output

{
    "merged": {
        "name": "object-deep-merge",
        "description": "merge objects, deeply"
    }
}

Simple Example w/ TData Generic

Note

Passing in TData will validate the shape of the objects passed in.

type Data = {
    name: string;
    description: string;
};

const base: Data = { name: "object-deep-merge", description: "merge objects" };

const overrides: Partial<Data> = { description: "merge objects, deeply" };

const merged: Partial<Data> = merge<Partial<Data>>(base, overrides);

// TData    = Partial<Data>
// TResult  = Data

console.log({ merged });

Output

{
    "merged": {
        "name": "object-deep-merge",
        "description": "merge objects, deeply"
    }
}

Simple Example w/ TData and TResult Generics

Note

Passing in TResult will override the output type. While this should be used sparingly, it provides a convenient approach for correctly typing partial types into complete types.

type Data = {
    name: string;
    description: string;
};

const base: Data = { name: "object-deep-merge", description: "merge objects" };

const overrides: Partial<Data> = { description: "merge objects, deeply" };

const merged: Data = merge<Partial<Data>, Data>(base, overrides);

// TData    = Partial<Data>
// TResult  = Data

console.log({ merged });

Output

{
    "merged": {
        "name": "object-deep-merge",
        "description": "merge objects, deeply"
    }
}