What does Array.filter do?
it does not change the array so needs to be assigned to a variable
What should the callback function return?
returns a boolean value if true returns a copy
What is Array.filter useful for?
to filter out unwanted arrays
What does Array.map do?
What should the callback function return?
What is Array.map useful for?
What does Array.reduce do?
walks through an array and reduces it down to a single value
What action should the callback function perform?
exam the element do a calculation and add it to the accumulated value and updates it.
What should the callback function return?
it returns the accumulated value
What is Array.reduce useful for?