1. What is scope? Your explanation should include the idea of global vs. block scope.

scope is the environment in which items like objects and functions are available. block scope, for example,
is the environment within a block, such as a for loop, a function, or an object. in block scope, variables are
considered 'local'. global scope is the environment that contains everything that wasn't declared inside of
a block. in vanilla js, this is typically the window object.

2. Why are global variables avoided?

global variables are avoided mainly because they can cause collisions, such as name conflicts with external resources,
other scripts, window properties, etc. they're also avoided because they're technically slower to reference than local
variables.

3. Explain JavaScript's strict mode

in strict mode, many things are changed to prevent certain behaviors. for example, if a variable is declared without
any variable keyword (like let, const, or var) in non-strict mode, that variable becomes a property in global namespace.
however, in strict mode, doing this just throws an error. also, assigning values to non-writable items like NaN (which just
fails silently in non-strict) throws an error. strict mode has many, many other features as well, mainly meant to prohibit
illegal / discourages practices in javascript.

4. What are side effects, and what is a pure function?

side effects are unintended behaviors of a script, usually as a result of mistakes that were made in writing: such as a function
modifying objects outside of its scope that it isn't meant to access.

a pure function has no side effects, and also always provides x output for y input every time it is called. an example of
a typical pure function would be a hashing algorithm.