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Working with prototype

importance: 5

Here’s the code that creates a pair of objects, then modifies them.

Which values are shown in the process?

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

alert( rabbit.jumps ); // ? (1)

delete rabbit.jumps;

alert( rabbit.jumps ); // ? (2)

delete animal.jumps;

alert( rabbit.jumps ); // ? (3)

There should be 3 answers.

  1. true, taken from rabbit.
  2. null, taken from animal.
  3. undefined, there’s no such property any more.