Noob mind-block: functions within functions.

The javascript array.sort() function by default will turn each item into a string and then sort them logically as strings unless a function is passed as the argument.

You can test this in the console

[10,44,32,1000,0,44,3,4].sort();
[0, 10, 1000, 3, 32, 4, 44, 44]

Now if you want to pass a function as an argument, the function must take 2 parameters. The standard community convention says to name them a and b, but you can name them whatever you want. The results of these two parameters should end up as one of three options.

1. A value less than zero if the first parameter is less than the second
2. A value greater than zero if the first parameter is greater than the second
3. Or, zero if both the first and second parameters are equal

So when we call

var myArray = [10, 44, 32, 1000, 0, 44, 3, 4];

myArray.sort(function(first, second) {
  return first - second;
});

the array will iterate over all its elements and try subtracting first from second. Depending on if the result is any positive number, any negative number, or 0 will dictate its place in the array.

So armed with this knowledge you can test it out in the console!

var myArray = [10, 44, 32, 1000, 0, 44, 3, 4];
myArray.sort(function(first, second) {
  var result = first - second;
  console.log("First is " + first + " and second is " + second + " so the result is " + result);
  return result;
});

Now... try reversing the sort order! It's pretty simple, but a fun challenge!