task-proto.js

let animal = {
  jumps: null
};
let rabbit = {
  jumps: true
};

rabbit.__proto__ = animal;

console.log( rabbit.jumps ); // ? (1)

delete rabbit.jumps;

console.log( rabbit.jumps ); // ? (2)

delete animal.jumps;

console.log( rabbit.jumps ); // ? (3)

/*
(1) true, property from rabbit.
(2) null, property from animal.
(3) undefined, doesn't have a property.
*/