What is scope? Your explanation should include the idea of global vs. local scope.
  Scope refers to the scale that variables will be able to affect.  Scope can be local or global.  Local variables only affect
  code within its function.  Global variables can affect code within the entire javascript file, or even multiple files.

Why are global variables avoided?
  Global variables affect all the code in a project and can cause problems if they are unintentionally referenced down the line.
  As a project gets bigger, global code can be harder to control and can cause problems that are difficult to find.

Explain JavaScript's strict mode
  Strict mode sends an `Uncaught ReferenceError` whenever you try to create a variable without its 'const' or 'let' keywords.
  This is very useful to keep yourself from using global variables without intending to.  To initiate strict mode you type in
  'use strict'; at the top of a javascript document.

What are side effects, and what is a pure function?
  Side effects can happen if your code produces unintended results.  Side effects can be caused by global variables affecting
  variables that you didn't intend to have interacting with each other.  A pure function is both determinate and doesn't have
  side effects.  Determinate functions are called so when it returns the same value every time the same input is given.