prototypalInheritanceOnBuiltInObjects.md

[JavaScript] - Prototypal Inheritance on Built-In Objects

const Person = function (firstName, birthYear) {
  this.firstName = firstName; // assign param to `this.firstName` property
  this.birthYear = birthYear;
};
const jonas = new Person('Jonas', 1991);

console.log(jonas.__proto__);
// Object.prototype (top of prototype chain)
console.log(jonas.__proto__.__proto__); // Object.prototype
console.log(jonas.__proto__.__proto__.__proto__); // null

console.dir(Person.prototype.constructor);

const arr = [3, 6, 6, 5, 6, 9, 9]; // new Array === []
console.log(arr.__proto__);
console.log(arr.__proto__ === Array.prototype);

console.log(arr.__proto__.__proto__); // Object.prototype

// add new function to Array.prototype
Array.prototype.unique = function () {
  return [...new Set(this)];
};

console.log(arr.unique());
// However, this is a bad practice, don't do this as:
// 1. the next version of JS might add a method with the same name with a different behavior
// 2. big team with multiple developers might accidentally create multiple methods with the same name