Before You Continue

Marcus is about to give a great explanation of how variable access (also known as scoping) works in JavaScript.

But his explanation assumes some existing knowledge which you may or may not have right now. If you're missing any of the assumed knowledge, don't worry.

Prerequisite Knowledge

Go through this list from top to bottom. If any of the topics listed are new to you (or if you'd just like a refresher) follow the instructions.

Prerequisite 1 - JavaScript basics

Topics: syntax, variables, comments, operators, conditionals, functions, events.

If you need to learn: take Udacity's Intro to JavaScript (15 - 20 hours).

If you need to review: read the Mozilla Developer Network JavaScript Basics tutorial (about 1 hour).

Prerequisite 2 - Loops in JavaScript

Topics: for loops, while loops, how and why to use loops.

If you need to learn: Take Codecademy's Introduction to For Loops in JavaScript (1-3 hours) and Introduction to While Loops in JavaScript (1-2 hours).

If you need to review: read the Mozilla Developer Network documentation on for loops and while loops (20-40 minutes total).

Prerequisite 3 - Functions in JavaScript

Topics: declaring functions in JavaScript, using parameters, avoiding repetition, basics of variable scoping.

If you need to learn: take Udacity's Intro to JavaScript (though you may be able to skip through some of the early topics in the course). (10 - 15 hours).

If you need to review: take Codecademy's Introduction to Functions in JS (about 1-2 hours).