Javascript: How to detect if browser window is scrolled to bottom?

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 to the new bottom. If they are not at the bottom, they are reading previous content higher on the page, so I don't want to auto-scroll them since they want to stay where they are.

How can I detect if a user is scrolled to the bottom of the page or if they have scrolled higher on the page?

Answers:

Answer
window.onscroll = function(ev) {
    if ((window.innerHeight + window.scrollY) >= document.body.offsetHeight) {
        // you're at the bottom of the page
    }
};

See demo

Answer

Updated code for all major browsers support (include IE10 & IE11)

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

The problem with the current accepted answer is that window.scrollY is not available in IE.

Here is a quote from mdn regarding scrollY:

For cross-browser compatibility, use window.pageYOffset instead of window.scrollY.

And a working snippet:

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

Based on @Raphaël's comment, there was a problem in mac due to a small offset.
The following updated condition works:

(window.innerHeight + window.pageYOffset) >= document.body.offsetHeight - 2

I didn't have the chance to test it further, if someone can comment about this specific issue it will be great.

Answer

The accepted answer did not work for me. This did:

window.onscroll = function(ev) {
    if ((window.innerHeight + window.scrollY) >= document.body.scrollHeight) {
      // you're at the bottom of the page
      console.log("Bottom of page");
    }
};

If you're looking to support older browsers (IE9) use the alias window.pageYOffset which has slightly better support.

Answer

I was searching for an answer but haven't found an exact one. Here is a pure javascript solution that works with latest Firefox, IE and Chrome at the time of this answer:

// document.body.scrollTop alone should do the job but that actually works only in case of Chrome.
// With IE and Firefox it also works sometimes (seemingly with very simple pages where you have
// only a <pre> or something like that) but I don't know when. This hack seems to work always.
var scrollTop = (document.documentElement && document.documentElement.scrollTop) || document.body.scrollTop;

// Grodriguez's fix for scrollHeight:
// accounting for cases where html/body are set to height:100%
var scrollHeight = (document.documentElement && document.documentElement.scrollHeight) || document.body.scrollHeight;

// >= is needed because if the horizontal scrollbar is visible then window.innerHeight includes
// it and in that case the left side of the equation is somewhat greater.
var scrolledToBottom = (scrollTop + window.innerHeight) >= scrollHeight;

// As a bonus: how to scroll to the bottom programmatically by keeping the horizontal scrollpos:
// Since window.innerHeight includes the height of the horizontal scrollbar when it is visible
// the correct vertical scrollTop would be
// scrollHeight-window.innerHeight+sizeof(horizontal_scrollbar)
// Since we don't know the visibility/size of the horizontal scrollbar
// we scroll to scrollHeight that exceeds the value of the
// desired scrollTop but it seems to scroll to the bottom with all browsers
// without problems even when the horizontal scrollbar is visible.
var scrollLeft = (document.documentElement && document.documentElement.scrollLeft) || document.body.scrollLeft;
window.scrollTo(scrollLeft, scrollHeight);
Answer

This works

window.onscroll = function() {
    var scrollHeight, totalHeight;
    scrollHeight = document.body.scrollHeight;
    totalHeight = window.scrollY + window.innerHeight;

    if(totalHeight >= scrollHeight)
    {
        console.log("at the bottom");
    }
}
Answer

I've just started looking at this and the answers here helped me, so thanks for that. I've expanded a little so that the code is safe all the way back to IE7:

Hope this proves useful for someone.

Here, have a Fiddle ;)

    <!DOCTYPE html>
<html>
<head>
    <style>
        div {
            height: 100px;
            border-bottom: 1px solid #ddd;
        }

        div:nth-child(even) {
            background: #CCC
        }

        div:nth-child(odd) {
            background: #FFF
        }

    </style>
</head>

<body>
<div></div><div></div><div></div><div></div><div></div><div></div><div></div>
<div></div><div></div><div></div><div></div><div></div><div></div><div></div>
<div></div><div></div><div></div><div></div><div></div><div></div><div></div>
<div></div><div></div><div></div><div></div><div></div><div></div><div></div>
<div></div><div></div><div></div><div></div><div></div><div></div><div></div>
</body>

<script type="text/javascript">
console.log("Doc Height = " + document.body.offsetHeight);
console.log("win Height = " + document.documentElement.clientHeight);
window.onscroll = function (ev) {
    var docHeight = document.body.offsetHeight;
    docHeight = docHeight == undefined ? window.document.documentElement.scrollHeight : docHeight;

    var winheight = window.innerHeight;
    winheight = winheight == undefined ? document.documentElement.clientHeight : winheight;

    var scrollpoint = window.scrollY;
    scrollpoint = scrollpoint == undefined ? window.document.documentElement.scrollTop : scrollpoint;

    if ((scrollpoint + winheight) >= docHeight) {
        alert("you're at the bottom");
    }
};
</script>
</html>
Answer

If you're setting height: 100% on some container <div id="wrapper">, then the following code works (tested in Chrome):

var wrapper = document.getElementById('wrapper');

wrapper.onscroll = function (evt) {
  if (wrapper.scrollTop + window.innerHeight >= wrapper.scrollHeight) {
    console.log('reached bottom!');
  }
}
Answer
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.

Answer

You can look into jquery's infinite scroll:

http://www.infinite-scroll.com/infinite-scroll-jquery-plugin/

Which sounds like it does what you're asking for, assuming you're willing to use the jquery library and not hoping for a strict pure JS method.

Answer

Surprisingly none of the solutions worked for me. I think it's because my css was messed up, and body didn't wrap around all of the content when using height: 100% (don't know why yet). However while looking for a solution I've came up with something well... basically the same, but maybe it's worth to look at - I'm new into programming so sorry if it's doing the same slower, is less supported or something like that...

window.onscroll = function(evt) {
  var check = (Element.getBoundingClientRect().bottom - window.innerHeight <= 0) ? true : false;
  if (check) { console.log("You're at the bottom!"); }
};
Answer
$(document).ready(function(){
    $('.NameOfYourDiv').on('scroll',chk_scroll);
});

function chk_scroll(e)
{
    var elem = $(e.currentTarget);
    if (elem[0].scrollHeight - elem.scrollTop() == elem.outerHeight()) 
    {
        alert("scrolled to the bottom");
    }

}
Answer

if you love jquery

$(window).scroll(function() {
  if($(window).scrollTop() + $(window).height() >= $(document).height()) {
    // doSomethingHere();
  }
});
Answer

Using defaultView and documentElement with functional code snippet embedded:

const { defaultView } = document;
const { documentElement } = document;
const handler = evt => requestAnimationFrame(() => {
  const hitBottom = (() => (defaultView.innerHeight + defaultView.pageYOffset) >= documentElement.offsetHeight)();
  hitBottom
    ? console.log('yep')
    : console.log('nope')
});
document.addEventListener('scroll', handler);
<pre style="height:110vh;background-color:fuchsia">scroll down</pre>

Answer
const handleScroll = () => {
    if (Math.round(window.scrollY + window.innerHeight) >= Math.round(document.body.scrollHeight)) {
        onScroll();
    }
};

This code worked for me in Firefox and IE as well.

Answer

I had to come up with a way (in Java) to systematically scroll down looking for a component for which I didn't know the correct XPath (long story, so just play along). As I just stated, I needed to scroll down while looking for a component and stop either when the component was found or the bottom of the page was reached.

The following code snippet controls the scrolling down to the bottom of the page:

JavascriptExecutor js = (JavascriptExecutor) driver;
boolean found = false;
long currOffset = 0;
long oldOffset = 0;
do
{
    oldOffset = currOffset;
    // LOOP to seek the component using several xpath regexes removed
    js.executeScript("window.scrollBy(0, 100)");
    currOffset = (Long)js.executeScript("var offset = window.window.pageYOffset; return offset;");
} while (!found && (currOffset != oldOffset));

By the way, the window is maximized before this code snippet is executed.

Answer

The accepted answer did not work for me. This did:

const element = document.createElement('div');
document.body.appendChild(element);
document.addEventListener('scroll', () => {
    const viewportHeight = window.innerHeight;
    const distance = element.getBoundingClientRect().top;
    if (Math.floor(distance) <= viewportHeight) {
        console.log('yep')
    } else {
        console.log('nope')
    }
})
Answer

You can check if the combined result of the window's height and scroll top is bigger than that of the body

if (window.innerHeight + window.scrollY >= document.body.scrollHeight) {}

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