jquery - How to determine if a div changes its height or any css attribute?
Please don't use techniques described in other answers here. They are either not working with css3 animations size changes, floating layout changes or changes that don't come from jQuery land. You can use a resize-detector, a event-based approach, that doesn't waste your CPU time.
https://github.com/marcj/css-element-queries
It contains a ResizeSensor class you can use for that purpose.
new ResizeSensor(jQuery('#mainContent'), function(){
console.log('main content dimension changed');
});
Disclaimer: I wrote this library
For future sake I'll post this. If you do not need to support < IE11 then you should use MutationObserver.
Here is a link to the caniuse js MutationObserver
Simple usage with powerful results.
var observer = new MutationObserver(function (mutations) {
//your action here
});
//set up your configuration
//this will watch to see if you insert or remove any children
var config = { subtree: true, childList: true };
//start observing
observer.observe(elementTarget, config);
When you don't need to observe any longer just disconnect.
observer.disconnect();
Check out the MDN documentation for more information
Another simple example.
For this sample we can use 100x100 DIV-box:
<div id="box" style="width: 100px; height: 100px; border: solid 1px red;">
// Red box contents here...
</div>
And small jQuery trick:
<script type="text/javascript">
jQuery("#box").bind("resize", function() {
alert("Box was resized from 100x100 to 200x200");
});
jQuery("#box").width(200).height(200).trigger("resize");
</script>
Steps:
- We created DIV block element for resizing operatios
- Add simple JavaScript code with:
- jQuery bind
- jQuery resizer with trigger action "resize" - trigger is most important thing in my example
- After resize you can check the browser alert information
That's all. ;-)
First, There is no such css-changes event out of the box, but you can create one by your own, as onchange
is for :input
elements only. not for css changes.
There are two ways to track css changes.
- Examine the DOM element for css changes every x time(500 milliseconds in the example).
- Trigger an event when you change the element css.
- Use the
DOMAttrModified
mutation event. But it's deprecated, so I'll skip on it.
First way:
var $element = $("#elementId");
var lastHeight = $("#elementId").css('height');
function checkForChanges()
{
if ($element.css('height') != lastHeight)
{
alert('xxx');
lastHeight = $element.css('height');
}
setTimeout(checkForChanges, 500);
}
Second way:
$('#mainContent').bind('heightChange', function(){
alert('xxx');
});
$("#btnSample1").click(function() {
$("#mainContent").css('height', '400px');
$("#mainContent").trigger('heightChange'); //<====
...
});
If you control the css changes, the second option is a lot more elegant and efficient way of doing it.
Documentations:
- bind:
Description: Attach a handler to an event for the elements.
- trigger:
Description: Execute all handlers and behaviors attached to the matched elements for the given event type.