125: JS Challenge 6

 Today's challenge was to hand-write a function that reduces an array. This function accepts a callback function and applies it to the elements of the array, and combines them into an accumulator variable. I accomplished this by declaring a variable, iterating over the array with a (for, of) loop, and summing their values into the accumulator to return. The built-in array method to achieve this is called Array.reduce. Reduce is a powerful method that can combine the functionality of both filter() and map().