Scoping in Javascript

Where and when variables will be accessible in your code.

Scoping is important because we want to as much as possible follow the Principle of Least Privilege when writing programs — that is, if you don’t need to reveal your variable to the rest of your program, then keep its scope isolated. This important for many reasons, including reducing the chance of creating bugs/side effects, and increasing the efficiency of garbage collecting of variables while your program is running.