element-resize-detector

Optimized cross-browser resize listener for elements. Up to 37x faster than related approaches (read section 5 of the article).

npm install element-resize-detector

Usage

Include the script in the browser:

<script src="node_modules/element-resize-detector/dist/element-resize-detector.min.js"></script>

This will create a global function elementResizeDetectorMaker, which is the maker function that makes an element resize detector instance.

You can also require it like so:

var elementResizeDetectorMaker = require("element-resize-detector");

Create instance

// With default options (will use the object-based approach).
var erd = elementResizeDetectorMaker();

// With the ultra fast scroll-based approach.
// This is the recommended strategy.
var erdUltraFast = elementResizeDetectorMaker({
  strategy: "scroll" //<- For ultra performance.
});

There is also an callOnAdd option, which determines if listeners should be called when they are getting added. Default is true. If true, the listener is guaranteed to be called when it has been added. If false, the listener will not be guarenteed to be called when it has been added (does not prevent it from being called).

API

listenTo(element, listener) or listenTo(options, element, listener)

Listens to the element for resize events and calls the listener function with the element as argument on resize events. Options passed to the function will override the instance options.

Example usage:

erd.listenTo(document.getElementById("test"), function(element) {
  var width = element.offsetWidth;
  var height = element.offsetHeight;
  console.log("Size: " + width + "x" + height);
});

removeListener(element, listener)

Removes the listener from the element.

removeAllListeners(element)

Removes all listeners from the element, but does not completely remove the detector. Use this function if you may add listeners later and don't want the detector to have to initialize again.

uninstall(element)

Completely removes the detector and all listeners.

initDocument(document)

If you need to listen to elements inside another document (such as an iframe), you need to init that document with this function. Otherwise the library won't be able to detect when elements are attached to the document. So for an iframe, simpy invoke erd.initDocument(iframe.contentDocument); when the iframe is mounted on the DOM for the first time. The document from which the element resize detector instance is created will be initialized automatically. Notice that a new document is created when an iframe loads its content. So for iframes, be sure you invoke this function for each onLoad iframe event.

Caveats

1. If the element has position: static it will be changed to position: relative. Any unintentional top/right/bottom/left/z-index styles will therefore be applied and absolute positioned children will be positioned relative to the element.
2. A hidden element will be injected as a direct child to the element.

Credits

Big thanks to Evry sponsoring this project.

This library is using the two approaches (scroll and object) as first described at http://www.backalleycoder.com/2013/03/18/cross-browser-event-based-element-resize-detection/.

The scroll based approach implementation was based on Marc J's implementation https://github.com/marcj/css-element-queries/blob/master/src/ResizeSensor.js.

Please note that both approaches have been heavily reworked for better performance and robustness.

Changelog

1.2.4

• Harden onExpandScroll and onShrinkScroll handlers. See #132

1.2.3

• Fix problems with object approach in FF. Revert #122.

1.2.2

• Fixes scroll strategy to account for elements within shadow root. See #127.
• Fix potential contenteditable bugs with object approach. See #122.

1.2.1

A release that includes 1.1.15 and 1.1.16 with 1.2.0.

1.2.0

• Add new method initDocument(document) which is needed when listening to detached elements in other documents, such as iframes.
• Add a new optional option that adds important! to most style properties, to avoid CSS overriding. Disabled by default.
• Fix an issue with the object approach in IE8. See #95.
• Fix uninstall issue with object approach. See #102.
• Fixed errornous optimization that prevented scrollbar repositioning for really fast x -> y -> x resizes.

1.1.16

• Fix bug that could happen during uninstall when waiting for unrendered objects. See #117.

1.1.15

• ADA compliance fix for object approach. See #105.

1.1.14

• Explicit use of window.getComputedStyle everywhere.

1.1.13

• Only notify listeners when actual size change happened (in the rare case when multiple scroll events happens for the same resize). See #86.

1.1.12

• Fixed an issue with embedded WebView's on Android and iOS (when getComputedStyle.width = null). See #74.
• Fixed an issue with unrendered iframe in FireFox. See #68.

1.1.11

• Cleaned up the development build tools.
• Updated dev dependencies.
• Fixed an issue when uninstalling an element, and then calling listenTo in the middle of an old resize event. See #61.

1.1.10

• Fixed so that injected scroll elements are flex: none. See #64.
• Fixed so that injected object element is not focusable. See #67.

1.1.9

• Fixed uninstall issue when callOnAdd being true. Also now removing onAnimationStart listener when uninstalling. See #49.

1.1.8

• Fixed a compatability issue with options.idHandler.get.

1.1.7

• Fixed some rare issues with uninstalling elements while preparing/resizing.

1.1.6

• Fixed an issue with the resize detector changing the dimensions of the target element in some browsers (e.g., IE and FireFox).

1.1.5

• Fixed an issue with having parent elements dir=RTL.

1.1.4

• Added extra safety styles to injected elements to make them more resilient to global CSS affecting them.

1.1.3

• Now uninstall supports being called with elements that haven't been initialized. uninstall simply ignores non-erd elements.
• uninstall now also supports a collection of elements.

1.1.2

• Fixed so that uninstall may be called directly after a listenTo call.
• Fixed a typo in the readme.
• Fixed an invalid test.

1.1.1

• Using window.getComputedStyle instead of relying on the method being available in the global scope. This enables this library to be used in simulated browser environments such as jsdom.

1.1.0

• Supporting inline elements
• Event-based solution for detecting attached/rendered events so that detached/unrendered elements can be listened to without polling
• Now all changes that affects the offset size of an element are properly detected (such as padding and font-size).
• Scroll is stabilized, and is the preferred strategy to use. The object strategy will be deprecated (and is currently only used for some legacy browsers such as IE9 and Opera 12).