The identifier
read-only property of the PerformanceElementTiming
interface returns the value of the elementtiming
attribute on the element.
In this example an <img>
element is being observed by adding the elementtiming
attribute. A PerformanceObserver
is registered to get all performance entries of type "element"
and the buffered
flag is used to access data from before observer creation. The value of elementtiming
is big-image
. Calling entry.identifier
therefore returns the string big-image
.
<img
src="image.jpg"
alt="a nice image"
elementtiming="big-image"
id="myImage" />
const observer = new PerformanceObserver((list) => {
list.getEntries().forEach((entry) => {
if (entry.identifier === "big-image") {
console.log(entry.naturalWidth);
}
});
});
observer.observe({ type: "element", buffered: true });