How to do infinite scrolling with javascript only without jquery

Question

I wish to implement infinite scrolling with javascript and without jquery.

I am new to javascript.

After searching all over the net, I have this code.

Answer 1

What about replacing this line of code:

if (getDocHeight() == getScrollXY()[1] + window.innerHeight)

with the following:

if (getDocHeight() - 20 <= getScrollXY()[1] + window.innerHeight) 

Where 20 is the number how much pxs from bottom you want the trigger to execute.

Fiddle