Object.assign() is a method that permit to merge two or more variables.
A simple example taken from documentation of Google Chrome.

// Merge an object into another
let first = { name: 'Tony' };
let last = { lastName: 'Stark' };
let person = Object.assign(first, last);

You can use also to convert an array to object (with spread operator)

const hash = Object.assign({}, ...array)
Object.assign() is useful also for **clone an object**

let obj = { person: 'Thor Odinson' };
let clone = Object.assign({}, obj);

The syntax is something like:

Object.assign(target, elementsToMergeInsideTarget)