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 });

{
    "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 great additions to this library. It is not unreasonable to use those types for your merge typing needs.

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 });

{
    "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 });

{
    "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 });

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