mutable-push-method.md

const ships = ['X-wing', 'TIE Fighter', 'Millenium Falcon']

// define newShips with ships reference
const newShips = ships

// push 'Destroyer' value to new array created
newShips.push('Destroyer')

// the original variable is updated too, because it is the original reference
console.log(ships)
// ['X-wing', 'TIE Fighter', 'Millenium Falcon', 'Destroyer']

// variable newShips was updated by the reference
console.log(newShips)
// ['X-wing', 'TIE Fighter', 'Millenium Falcon', 'Destroyer']