What is Object.seal() in Javascript?

This is a very interesting method, similar to Object.freeze(), but only limiting the ability to add or remove properties.
const cat = {
  name: `Fifi`
};

Object.seal(cat);
console.log(cat);
// => {name: "Fifi"}

cat.name = `Mimi`;
console.log(cat);
// => {name: "Mimi"}

cat.breed = `Chartreux`;
console.log(cat);
// => {name: "Mimi"}
As you can see, breed property has not been added, but the name property's value could be changed.