You can either use dot notation (.) or square bracket ([]) notation to add a new property to a JavaScript object.

const fruits = {
    orange: '🍊',
    lemon: '🍋',
    mango: '🥭'
}

// Dot Notation
fruits.kiwi = '🥝'

// Square Bracket Notation
fruits['kiwi'] = '🥝'

console.log(fruits)
// { orange: '🍊', lemon: '🍋', mango: '🥭', kiwi: '🥝' }