To fix the error, start by creating a new function called
updateElement. You may recall that we added this to the body's
onscroll method. Now that we have distributed our objects in a random fashion on the screen and created a smooth scroll effect, we need to work on making things change at different rates as we scroll through the rows. This is the meat and potatoes of the parallax effect. In the end, when you scroll through the page, the objects can be programmed to move at different velocities.
This part will involve some fancy footwork and will be explained in a few steps, but it will be lightweight and easy to extend later as you please. The following code contains a function that will be run on every scroll, ...