javascript-detect-element-resize

A Cross-Browser, Event-based, Element Resize Detection.

In short, this implementation does NOT use an internal timer to detect size changes (as most implementations I found do). It uses scroll events on most browsers, and the onresize event on IE10 and below.

The method used not only detects javascript generated resize changes but also changes made from CSS pseudo classes e.g. :hover, CSS animations, etc.

About the libraries

I was searching for a library that allowed me to detect when an DOM element changes size, and all solutions I found had two problems:

only available as jQuery libraries (so no standalone Javascript)
all had terrible performance (because all of them use timers to intermittently poll the size of the elements to detect a change).

Then I came across this great post on Back Alley Coder about using ~~overflow and underflow events~~ scroll events to do event-based element resize detection; and it works great without consuming resources at all (just like any other browser originated event).

The libraries on this repository are just a ready-to-use implementation of the above, one pure javascript and the other a jQuery plugin version (just for convenience).

Libraries

Pure Javascript library usage

<script type="text/javascript" src="detect-element-resize.js"></script>
<script type="text/javascript">
  var resizeElement = document.getElementById('resizeElement'),
      resizeCallback = function() {
          /* do something */
      };
  addResizeListener(resizeElement, resizeCallback);
  removeResizeListener(resizeElement, resizeCallback);
</script>

jQuery plugin library usage

<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript" src="jquery.resize.js"></script>
<script type="text/javascript">
  var myFunc = function() {
    /* do something */
  };
  
  $('#resizeElement').resize(myFunc);
  $('#resizeElement').removeResize(myFunc);
</script>

Compatibility

Works great on:

Chrome
Firefox
IE 11 and below (tested on 11, 10, 9, 8 and 7)

Known Issues:

On IE 10 and below: If you detach the element and re-attach it, you will need to add the resize listener again.

Doesn't work on:

Please let me know if you test these libraries on any other browser, of if you run into issues with any of the above browsers.

TODO

Fix detach/re-attach issue on IE 10 and below (IE 9 and below doesn't support CSS animations so we can use those as in the rest of the browsers).
Create minified version of the libraries.
Add support for standard jQuery bind method on 'resize' event.

Release Notes

v0.5.3

Fix for when the element is inside a display:none, and for when it is detached and reattached (changed @thomassuckow and @jerjou fixes to properly use CSS animations)
Adding /tests/ with some general QUnit tests to help test on multiple browsers

v0.5.2

Adding a bower.json file (thanks @adamjcook)
Fix style being appended to head multiple times (thanks @thomassuckow and @progman32)
Work around a chrome bug that would show scrollbars in some cases (thanks @thomassuckow)

v0.5.1

Fix for resize event on IE

v0.5

It is now fully compatible with IE11.
Rework of the libraries using the new scroll-event-based code of Back Alley Coder. For the pure javascript version I pretty much used the original code from Back Alley Coder and only had to add code to dynamically insert the styling for the resize-triggers.

v0.4.1

Fix for jQuery 'resize' method overlapping.

v0.4

Adds better cross-browser support, it now uses MutationObservers only on IE11.

v0.3

Adds support for MutationObservers.
Adds support for IE 11.
Wrapped the pure javascript version of the library (to hide non-public methods).

v0.2

Adds support for IE 8 and below.

v0.1

Implementation based on the works of Back Alley Coder.
Adds jQuery plugin version.

References

Similar libraries (but they use timers)

jQuery-mutate

jQuery-resize-plugin

Don't get me wrong, these are great libraries and work as advertised, it's just that they are not easy on browser resources.

External links

Back Alley Coder: Cross-Browser, Event-based, Element Resize Detection
Back Alley Coder: Overflow and Underflow Events

npm