1. Spot the Bug

Arrow function as constructor

const Animal = (name, age) => {
  this.name = name;
  this.age = age;
};

Animal.prototype.birthday = function () {
  this.age++;
};

const animal = new Animal('Leo', 'Lion');

Bug Details

• Arrow functions don't have their own this keyword. So, adding properties will leads to Error.
• we can't add property on function prototype if it's arrow function. Again no this keyword.
• we cannot use new keyword on arrow function. This will throw error X is not a constructor