Understanding var, let and const in JavaScript

Learn how var, let, and const behave differently in JavaScript. This beginner-friendly lesson uses execution context diagrams to show why var initializes with undefined while let and const do not, and what that means for accessing variables before their declaration. You will follow a step-by-step walkthrough of a code snippet, seeing exactly when each variable is created and when it becomes usable. By the end, you’ll understand the temporal dead zone and how to avoid common reference errors. Timeline 0:00 Introduction to the exercise 0:47 Error with let variables 1:32 Function declaration overwrites 2:19 Temporal dead zone error 3:05 Function expression hoisting error 3:50 var initialization in a new scope 4:38 Final example with let and closure Explore more at AltCampus: https://altcampus.com