[removed] How to detect if browser window is scrolled to bottom?

Question

I need to detect if a user is scrolled to the bottom of a page. If they are at the bottom of the page, when I add new content to the bottom, I will automatically scroll them

Answer 1

window.onscroll = function(ev) {
    if ((window.innerHeight + Math.ceil(window.pageYOffset)) >= document.body.offsetHeight) {
        alert("you're at the bottom of the page");
    }
};

This Answer will fix edge cases, this is because pageYOffset is double while innerHeight and offsetHeight are long, so when the browser gives you the info, you may be a pixel short. For example: on bottom of the page we have

true window.innerHeight = 10.2

true window.pageYOffset = 5.4

true document.body.offsetHeight = 15.6

Our calculation then becomes: 10 + 5.4 >= 16 which is false

To fix this we can do Math.ceil on the pageYOffset value.

Hope that helps.