Published Dec 4, 2023
Contribute to Docs

The Object.assign() method is used to modify a “destination” object with the contents of one or more objects passed to the method. If there are duplicate keys between the objects the values in the destination object will be overridden in the assignment.


Object.assign(destinationObj, sourceObj)
// Or
Object.assign(destinationObj, sourceObj, ... nObj)
  • destinationObj: The object to be modified. The entries of the other objects passed will be added to this object.
  • sourceObj: The object(s) that will be used to supplement the “destination” object.


The following code demonstrates a basic implementation of the Object.assign() method:

const eastLibrary = {
1: 'Green Eggs and Ham',
2: 'Cat in the Hat',
3: 'Hop on Pop',
const westLibrary = {
3: 'Lorax',
4: 'How the Grinch Stole Christmas',
5: 'The Zax',
const seussBooks = Object.assign(eastLibrary, westLibrary);

This will return the following output:

'1': 'Green Eggs and Ham',
'2': 'Cat in the Hat',
'3': 'Lorax',
'4': 'How the Grinch Stole Christmas',
'5': 'The Zax'

Note: The reassignment in the code above is optional. The following is true: eastLibrary === suessBooks.

All contributors

Looking to contribute?

Learn JavaScript on Codecademy