The spread operator can expand(spread) any iterable like an array or a string.

es6-spread-operator.js

const avengers = ['Thor', 'The Hulk', 'Captain America'];
let guardians = ['Star Lord', 'Gamorra', 'Drax', 'Rocket', 'Groot'];
// Spread out arrays in a new array and put a new value in between them
const heroes = [...avengers, 'Loki', ...guardians];

// Adding new stuff to an array just got easier too
guardians = [...guardians, 'Mantis', 'Yondu', 'Nebula'];

// Or simply making a TRUE copy of an array
const avengersCopy = [...avengers];

// We can also get everything out of an array in an object
const xmen = {
    team: 'Marvel',
    leader: 'Xavier',
    members: ['Jean Grey', 'Cyclopse', 'Beast', 'Gambit', 'Rogue', 'Wolverine'],
}

// This creates another true copy of the Array with new values in it. 
const xMenSpecial = ['Gambit', 'Mystique', 'Magneto', ...xmen.members];