How to get height of entire document with JavaScript?

user_72065 0
Viewed 596530

Some documents I can't get the height of the document (to position something absolutely at the very bottom). Additionally, a padding-bottom on seems to do nothing on these pages, but do on the pages where height will return. Case(s) in point:

http://fandango.com
http://paperbackswap.com

On Fandango
jQuery's $(document).height(); returns correct value
document.height returns 0
document.body.scrollHeight returns 0

On Paperback Swap:
jQuery's $(document).height(); TypeError: $(document) is null
document.height returns an incorrect value
document.body.scrollHeight returns an incorrect value

Note: I have browser level permissions, if there is some trick there.

javascript
13 Answers

Document sizes are a browser compatibility nightmare because, although all browsers expose clientHeight and scrollHeight properties, they don't all agree how the values are calculated.

There used to be a complex best-practice formula around for how you tested for correct height/width. This involved using document.documentElement properties if available or falling back on document properties and so on.

The simplest way to get correct height is to get all height values found on document, or documentElement, and use the highest one. This is basically what jQuery does:

var body = document.body,
    html = document.documentElement;

var height = Math.max( body.scrollHeight, body.offsetHeight, 
                       html.clientHeight, html.scrollHeight, html.offsetHeight );

A quick test with Firebug + jQuery bookmarklet returns the correct height for both cited pages, and so does the code example.

Note that testing the height of the document before the document is ready will always result in a 0. Also, if you load more stuff in, or the user resizes the window, you may need to re-test. Use onload or a document ready event if you need this at load time, otherwise just test whenever you need the number.

Borgar_273880

I lied, jQuery returns the correct value for both pages $(document).height();... why did I ever doubt it?

user_720650

The proper answer for 2017 is:

document.documentElement.getBoundingClientRect().height

Unlike document.body.scrollHeight this method accounts for body margins. It also gives fractional height value, which can be useful in some cases

user_3325280

For anyone having trouble scrolling a page on demand, using feature detection, I've come up with this hack to detect which feature to use in an animated scroll.

The issue was both document.body.scrollTop and document.documentElement always returned true in all browsers.

However you can only actually scroll a document with either one or the other. d.body.scrollTop for Safari and document.documentElement for all others according to w3schools (see examples)

element.scrollTop works in all browsers, not so for document level.

    // get and test orig scroll pos in Saf and similar 
    var ORG = d.body.scrollTop; 

    // increment by 1 pixel
    d.body.scrollTop += 1;

    // get new scroll pos in Saf and similar 
    var NEW = d.body.scrollTop;

    if(ORG == NEW){
        // no change, try scroll up instead
        ORG = d.body.scrollTop;
        d.body.scrollTop -= 1;
        NEW = d.body.scrollTop;

        if(ORG == NEW){
            // still no change, use document.documentElement
            cont = dd;
        } else {
            // we measured movement, use document.body
            cont = d.body;
        }
    } else {
        // we measured movement, use document.body
        cont = d.body;
    }
user_17491410

I don't know about determining height just now, but you can use this to put something on the bottom:

<html>
<head>
<title>CSS bottom test</title>
<style>
.bottom {
  position: absolute;
  bottom: 1em;
  left: 1em;
}
</style>
</head>

<body>

<p>regular body stuff.</p>

<div class='bottom'>on the bottom</div>

</body>
</html>
user_543220
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