- Use forEach to get data and concatenate firstname and lastname
- use map to get data and return a new array of uppercase firstnames
- use filter to get all user with their shirt size set to L
- use reduce to sum all the donations

- create callback display to test and console.log the results of our function solution
- pass arr.length as an argument on getLength return callback  and pass array items and callback display as arguments on getLength invocation
- pass the last item as an argument on last function return callback and pass array items and callback display as arguments on last function invocation
- pass the sum of x and y as an argument on sumNums function return callback and pass the values of x, y  and callback display as arguments on sumNums invocation
- pass the multiply of x and y as an argument on multiplyNums function return callback and pass the values of x, y  and callback display as arguments on multiplyNums invocation
- use include array method to check if item is in array and pass the boolean value into the callback as an argument, invoking the contains function with the item to check, the items array and the callback function
- update README.md

- write simple example of a closure and invoke function
- Counter Function:
    -- declare count variable and set it to zero
    -- return a function that increments the count variable.
    -- assign return value of counter function to new counter
    -- invoke new counter 4 times to show increment
- Counter Factory:
    -- declare variable count and set it to 0
    -- counterFactory return object containing methods increment and decrement
    -- increment is a method that adds one to count and returns count
    -- decrement is a method that removes one from count and returns count
    -- set counterFactory return value to counterFactoryItems
    -- invoke increment 3times and decrememnt 2times to test functions.
- update README.md

- output fullname and donation of top donors
- total donations by donors from Skinix company
- output all email for runners in the array
- update README.md

- use filter and index of methods to remove duplicates
- pass the free array as a value on the callback
- invoke removeDuplicates passing items array and a callback to output result as an argument

Challenge on JavaScript II (Arrays, Closures, Callbacks)