Variable Scope Questions

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What is scope? Your explanation should include the idea of global vs. block scope.
  Scope is how the variables within your code can or can't be accessed at different points within your code. Global scope is
  when a variable can be accessed from anywhere within your code. This means that any code not declared within block code can
  be accessed globally. Block scope is when variables can only be accessed within a function and outside of that function 
  they don't exist. 
  
Why are global variables avoided?
  Global variables are avoided because they can have unintended consequences on other areas of the code. If a global variable
  were to be used in a function without the use of "let" or "const", that global would be accessed and altered which would 
  then change any other functions that access that global variable. 
  
Explain JavaScript's strict mode
  Strict Mode is something that the programmer can write into the beginning of the code that allows Javascript to throw an 
  error code whenever a variable is declared without the use of let" or "const".
  
What are side effects, and what is a pure function?
  Side effects are when a function goes outside its local scope up into a parent scope and alters a value that lives there.
  A pure function is when a function will always return the same value if it's provided with the same inputs without any
  side effects.