Also, I used sort to solve this one as well, so it will work, but I think my code is less than elegant I looked up reduce and you might want to try P1xt’s way.
On the sub-arrays: I was able to run the array through a for loop, then set each sub-array by remembering that the first sub-array is actually arr[0], the second sub-array is arr[1] etc…
A problem I see is that you are creating a variable called largestOfFour and setting the array values within your function and this won’t work in the long term. Since arr is the parameter being fed in, use that to hold your original array. You don’t need to set it, it comes pre-filled
Use a for loop to iterate through arr using arr.length and set a sub-array variable to equal each sub-array (which are arr[0], arr[1], arr[2], arr[3]).