Remove properties with delete:
let user = { name: "Alice", age: 30, temp: true }
delete user.temp
console.log(user) // { name: "Alice", age: 30 }
console.log(user.temp) // undefined
delete returns true in most cases, even for properties that don't exist. It only returns false for non-configurable properties. Avoid delete in performance-sensitive code. Setting to undefined is faster but keeps the key.