The Iterator interface defines a standard way to access elements of a collection one at a time. It’s the mechanism that powers for…of loops, spread syntax, and destructuring in JavaScript. A Quick Look at the Example Key idea: An iterator is an object with a next() method that returns { value, done } on each…

Polymorphism means “many forms” — it’s the ability of different classes to respond to the same method call in their own way. It’s one of the four pillars of object-oriented programming (along with encapsulation, inheritance, and abstraction). A Quick Look at the Example Key idea: animal.speak() looks identical for every animal, but produces a different…

Method overriding is when a subclass provides its own implementation of a method that already exists in its parent class. The subclass’s method “takes over” — when called on an instance of the subclass, the new method runs instead of the parent’s. A Quick Look at the Example a. What is Method Overriding? Method overriding…

Class inheritance allows you to create a new class that inherits properties and methods from an existing class. The new class (subclass/child) can reuse, extend, or override the behavior of the parent class (superclass/base). A Quick Look at the Example a. What is Class Inheritance? Inheritance is a mechanism where one class (the subclass or…

Comments are used to explain your code or disable a portion of it. They are ignored by JavaScript and are purely for humans (including your future self). Overview of Comment Types Type Syntax Use Case Single-line // comment Brief explanations, inline notes Multi-line /* comment */ Longer explanations, disabling code blocks a. JavaScript Comments Comments…