ResizeObserverEntry
The ResizeObserverEntry
interface represents the object passed to the ResizeObserver()
constructor's callback function, which allows you to access the new dimensions of the Element
or SVGElement
being observed.
Instance properties
ResizeObserverEntry.borderBoxSize
Read only-
An object containing the new border box size of the observed element when the callback is run.
ResizeObserverEntry.contentBoxSize
Read only-
An object containing the new content box size of the observed element when the callback is run.
ResizeObserverEntry.devicePixelContentBoxSize
Read only-
An object containing the new content box size in device pixels of the observed element when the callback is run.
ResizeObserverEntry.contentRect
Read only-
A
DOMRectReadOnly
object containing the new size of the observed element when the callback is run. Note that this is better supported than the above two properties, but it is left over from an earlier implementation of the Resize Observer API, is still included in the spec for web compat reasons, and may be deprecated in future versions. ResizeObserverEntry.target
Read only-
A reference to the
Element
orSVGElement
being observed.
Note: The content box is the box in which content can be placed, meaning the border box minus the padding and border width. The border box encompasses the content, padding, and border. See The box model for further explanation.
Instance methods
None.
Examples
The following snippet is taken from the resize-observer-text.html (see source) example. This uses a simple feature detection test to see if the browser supports the newer contentBoxSize
property — if so, it uses that to get the sizing data it needs. If not, it uses the older contentRect
property.
js
const resizeObserver = new ResizeObserver((entries) => {
for (const entry of entries) {
if (entry.contentBoxSize) {
h1Elem.style.fontSize = `${Math.max(
1.5,
entry.contentBoxSize.inlineSize / 200
)}rem`;
pElem.style.fontSize = `${Math.max(
1,
entry.contentBoxSize.inlineSize / 600
)}rem`;
} else {
h1Elem.style.fontSize = `${Math.max(
1.5,
entry.contentRect.width / 200
)}rem`;
pElem.style.fontSize = `${Math.max(1, entry.contentRect.width / 600)}rem`;
}
}
});
resizeObserver.observe(divElem);
Specifications
Specification |
---|
Resize Observer # resize-observer-entry-interface |
Browser compatibility
BCD tables only load in the browser