How to detect DIV's dimension changed?
I've the following sample html, there is a DIV which has 100% width. It contains some elements. While performing windows re-sizing, the inner elements may be re-positioned, and the dimension of the div may change. I'm asking if it is possible to hook the div's dimension change event? and How to do that? I currently bind the callback function to the jQuery resize event on the target DIV, however, no console log is outputted, see below:
<html>
<head>
<script type="text/javascript" language="javascript" src="http://code.jquery.com/jquery-1.6.1.min.js"></script>
<script type="text/javascript" language="javascript">
$('#test_div').bind('resize', function(){
console.log('resized');
});
</script>
</head>
<body>
<div id="test_div" style="width: 100%; min-height: 30px; border: 1px dashed pink;">
<input type="button" value="button 1" />
<input type="button" value="button 2" />
<input type="button" value="button 3" />
</div>
</body>
</html>
A new standard for this is the Resize Observer api, available in Chrome 64.
function outputsize() {
width.value = textbox.offsetWidth
height.value = textbox.offsetHeight
}
outputsize()
new ResizeObserver(outputsize).observe(textbox)Width: <output id="width">0</output><br>
Height: <output id="height">0</output><br>
<textarea id="textbox">Resize me</textarea><br>Resize Observer
Documentation: https://developer.mozilla.org/en-US/docs/Web/API/Resize_Observer_API
Spec: https://wicg.github.io/ResizeObserver
Current Support: http://caniuse.com/#feat=resizeobserver
Polyfills: https://github.com/pelotoncycle/resize-observer https://github.com/que-etc/resize-observer-polyfill https://github.com/juggle/resize-observer
There is a very efficient method to determine if a element's size has been changed.
http://marcj.github.io/css-element-queries/
This library has a class ResizeSensor which can be used for resize detection.
It uses an event-based approach, so it's damn fast and doesn't waste CPU time.
Example:
new ResizeSensor(jQuery('#divId'), function(){
console.log('content dimension changed');
});
Please do not use the jQuery onresize plugin as it uses setTimeout() in combination with reading the DOM clientHeight/clientWidth properties in a loop to check for changes.
This is incredible slow and inaccurate since it causes layout thrashing.
Disclosure: I am directly associated with this library.
Long term, you will be able to use the ResizeObserver.
new ResizeObserver(callback).observe(element);
Unfortunately it is not currently supported by default in many browsers.
In the mean time, you can use function like the following. Since, the majority of element size changes will come from the window resizing or from changing something in the DOM. You can listen to window resizing with the window's resize event and you can listen to DOM changes using MutationObserver.
Here's an example of a function that will call you back when the size of the provided element changes as a result of either of those events:
var onResize = function(element, callback) {
if (!onResize.watchedElementData) {
// First time we are called, create a list of watched elements
// and hook up the event listeners.
onResize.watchedElementData = [];
var checkForChanges = function() {
onResize.watchedElementData.forEach(function(data) {
if (data.element.offsetWidth !== data.offsetWidth ||
data.element.offsetHeight !== data.offsetHeight) {
data.offsetWidth = data.element.offsetWidth;
data.offsetHeight = data.element.offsetHeight;
data.callback();
}
});
};
// Listen to the window's size changes
window.addEventListener('resize', checkForChanges);
// Listen to changes on the elements in the page that affect layout
var observer = new MutationObserver(checkForChanges);
observer.observe(document.body, {
attributes: true,
childList: true,
characterData: true,
subtree: true
});
}
// Save the element we are watching
onResize.watchedElementData.push({
element: element,
offsetWidth: element.offsetWidth,
offsetHeight: element.offsetHeight,
callback: callback
});
};
ResizeSensor.js is part of a huge library, but I reduced its functionality to THIS:
function ResizeSensor(element, callback)
{
let zIndex = parseInt(getComputedStyle(element));
if(isNaN(zIndex)) { zIndex = 0; };
zIndex--;
let expand = document.createElement('div');
expand.style.position = "absolute";
expand.style.left = "0px";
expand.style.top = "0px";
expand.style.right = "0px";
expand.style.bottom = "0px";
expand.style.overflow = "hidden";
expand.style.zIndex = zIndex;
expand.style.visibility = "hidden";
let expandChild = document.createElement('div');
expandChild.style.position = "absolute";
expandChild.style.left = "0px";
expandChild.style.top = "0px";
expandChild.style.width = "10000000px";
expandChild.style.height = "10000000px";
expand.appendChild(expandChild);
let shrink = document.createElement('div');
shrink.style.position = "absolute";
shrink.style.left = "0px";
shrink.style.top = "0px";
shrink.style.right = "0px";
shrink.style.bottom = "0px";
shrink.style.overflow = "hidden";
shrink.style.zIndex = zIndex;
shrink.style.visibility = "hidden";
let shrinkChild = document.createElement('div');
shrinkChild.style.position = "absolute";
shrinkChild.style.left = "0px";
shrinkChild.style.top = "0px";
shrinkChild.style.width = "200%";
shrinkChild.style.height = "200%";
shrink.appendChild(shrinkChild);
element.appendChild(expand);
element.appendChild(shrink);
function setScroll()
{
expand.scrollLeft = 10000000;
expand.scrollTop = 10000000;
shrink.scrollLeft = 10000000;
shrink.scrollTop = 10000000;
};
setScroll();
let size = element.getBoundingClientRect();
let currentWidth = size.width;
let currentHeight = size.height;
let onScroll = function()
{
let size = element.getBoundingClientRect();
let newWidth = size.width;
let newHeight = size.height;
if(newWidth != currentWidth || newHeight != currentHeight)
{
currentWidth = newWidth;
currentHeight = newHeight;
callback();
}
setScroll();
};
expand.addEventListener('scroll', onScroll);
shrink.addEventListener('scroll', onScroll);
};
How to use it:
let container = document.querySelector(".container");
new ResizeSensor(container, function()
{
console.log("dimension changed:", container.clientWidth, container.clientHeight);
});
You have to bind the resize event on the window object, not on a generic html element.
You could then use this:
$(window).resize(function() {
...
});
and within the callback function you can check the new width of your div calling
$('.a-selector').width();
So, the answer to your question is no, you can't bind the resize event to a div.