extend (Lodash Compatibility)

::: warning Use Object.assign() instead

This extend function performs slower due to complex logic that handles properties inherited from the prototype chain.

Use the faster and more modern Object.assign() instead.

:::

Copies own and inherited properties from source objects to a target object.

const result = extend(object, source);

Usage

extend(object, ...sources)

Use extend to copy properties from one object to another. Similar to Object.assign(), but also copies inherited properties. This function is an alias of assignIn.

import { extend } from 'es-toolkit/compat';

// Copy basic properties
const target = { a: 1 };
extend(target, { b: 2 }, { c: 3 });
// Returns: { a: 1, b: 2, c: 3 }

// Also copies inherited properties
function Parent() {
  this.a = 1;
}
Parent.prototype.b = 2;

const source = new Parent();
extend({}, source);
// Returns: { a: 1, b: 2 }

When there are duplicate properties, later source objects overwrite earlier ones.

import { extend } from 'es-toolkit/compat';

extend({ a: 1, b: 2 }, { b: 3 }, { c: 4 });
// Returns: { a: 1, b: 3, c: 4 }

Parameters

• object (any): The target object to receive properties.
• ...sources (any[]): The source objects that provide properties.

Returns

(any): Returns the object with copied properties. The first argument object is modified.