What is object.assign?
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
lodash.assign
Lodash's _.assign() method performs a similar function to object.assign, allowing you to copy properties from source objects to a target object. Lodash offers more extensive utility functions, making it a more heavyweight option compared to the focused functionality of object.assign.
extend
The extend package is another alternative that can be used to merge the properties of two or more objects together into the first object. It's similar to object.assign but also supports deep copying with an additional argument.
#object.assign 



An Object.assign shim. Invoke its "shim" method to shim Object.assign if it is unavailable.
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 = Object.assign || require('object.assign');
Example
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
};
var assign = require('object.assign');
var assert = require('assert');
assign(target, source1, source2, sourceN);
assert.deepEqual(target, expected);
var assign = require('object.assign');
var assert = require('assert');
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);
assert.deepEqual(assigned, {
a: true,
b: true,
c: false,
d: false,
e: false
});
var assign = require('object.assign');
var assert = require('assert');
delete Object.assign;
var shimmedAssign = 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));
var assign = require('object.assign');
var assert = require('assert');
var shimmedAssign = 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