Practice merging and updating:
let defaults = {
theme: "light",
fontSize: 14,
notifications: true
}
let userPrefs = {
theme: "dark",
fontSize: 16
}
// Merge with user preferences taking priority
let settings = { ...defaults, ...userPrefs }
console.log(settings)
// { theme: "dark", fontSize: 16, notifications: true }
// Update single property
let updated = { ...settings, notifications: false }