Rouillie Wilkerson10,319 Points
Let vs Var...
Steven Parker174,098 Points
Some of the videos have not been revised for a while. Since ES6 (2015), "let" and "const" have become the common choices for variable declarations. "Const" is preferred when possible, and "let" if the variable will be changed.
Just be aware that they both have block scope, and are not hoisted. Use "var" if you need hoisting or function scope (but with good planning, neither should be necessary).
I'll admit that personally, I still like to use "var" for global variables just as a way to distinguish them at first glance.