What is scope? Your explanation should include the idea of global vs. local scope.
Scope is where a piece of code takes effect. This is commonly seen in variables. For instance a for loop can create a
variable the use for its execution but when you try to access that variable name outside the loop, it is non-existant.

Why are global variables avoided?
Global variables are avoided because they can cause confusion throughout the code.
For instance when a global variable is changed, yet the creator/maintenence coders expect it to be set to a certain value,
the can often change throughout the code.

Explain JavaScript's strict mode
Strict mode is used (and useful) to help write maintainable,
code by eliminating coloqualisism such as ending semicolons or var declarations.

What are side effects, and what is a pure function?
Side effects is what happens when a piece of code written has additional results other than what is intended.
This can be both good and bad.
A pure function is function that not only has no side effects but also doesn’t rely on side effects. EloquentJavascript

Explain variable hoisting in JavaScript.
Hoisting is how the JS interpreter searches for all veriable declarations,
moves it to the top of the scope its contained in, processes the rest of that code and exits.