The object.assign npm package is a polyfill for the Object.assign() method in JavaScript, which is used to copy the values of all enumerable own properties from one or more source objects to a target object. It returns the target object. This package provides a reliable way to use Object.assign() in environments that do not natively support it.

What are object.assign's main functionalities?

Copying properties

This feature allows you to copy the properties from one or more source objects to a target object. The target object is then returned by the function.

const object = require('object.assign').getPolyfill();
const target = { a: 1 };
const source = { b: 2 };
const returnedTarget = object(target, source);
console.log(target); // Output: { a: 1, b: 2 }

Merging objects

This feature demonstrates how to merge multiple objects into a new object. This is useful for combining properties from several objects into a single object.

const object = require('object.assign').getPolyfill();
const obj1 = { a: 1 };
const obj2 = { b: 2 };
const obj3 = { c: 3 };
const newObj = object({}, obj1, obj2, obj3);
console.log(newObj); // Output: { a: 1, b: 2, c: 3 }

Other packages similar to object.assign

Readme

Source

object.assign

An Object.assign shim. Invoke its "shim" method to shim Object.assign if it is unavailable.

This package implements the es-shim API interface. It works in an ES3-supported environment and complies with the spec. In an ES6 environment, it will also work properly with Symbols.

Takes a minimum of 2 arguments: target and source. Takes a variable sized list of source arguments - at least 1, as many as you want. Throws a TypeError if the target argument is null or undefined.

Most common usage:

var assign = require('object.assign').getPolyfill(); // returns native method if compliant
	/* or */
var assign = require('object.assign/polyfill')(); // returns native method if compliant

Example

var assert = require('assert');

// Multiple sources!
var target = { a: true };
var source1 = { b: true };
var source2 = { c: true };
var sourceN = { n: true };

var expected = {
	a: true,
	b: true,
	c: true,
	n: true
};

assign(target, source1, source2, sourceN);
assert.deepEqual(target, expected); // AWESOME!

var target = {
	a: true,
	b: true,
	c: true
};
var source1 = {
	c: false,
	d: false
};
var sourceN = {
	e: false
};

var assigned = assign(target, source1, sourceN);
assert.equal(target, assigned); // returns the target object
assert.deepEqual(assigned, {
	a: true,
	b: true,
	c: false,
	d: false,
	e: false
});

/* when Object.assign is not present */
delete Object.assign;
var shimmedAssign = require('object.assign').shim();
	/* or */
var shimmedAssign = require('object.assign/shim')();

assert.equal(shimmedAssign, assign);

var target = {
	a: true,
	b: true,
	c: true
};
var source = {
	c: false,
	d: false,
	e: false
};

var assigned = assign(target, source);
assert.deepEqual(Object.assign(target, source), assign(target, source));

/* when Object.assign is present */
var shimmedAssign = require('object.assign').shim();
assert.equal(shimmedAssign, Object.assign);

var target = {
	a: true,
	b: true,
	c: true
};
var source = {
	c: false,
	d: false,
	e: false
};

assert.deepEqual(Object.assign(target, source), assign(target, source));

Tests

Simply clone the repo, npm install, and run npm test

Keywords

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Last updated on 16 Aug 2022

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