PerformanceElementTiming

{{APIRef("Performance API")}} {{SeeCompatTable}} 

The PerformanceElementTiming interface contains render timing information for image and text node elements the developer annotated with an elementtiming attribute for observation.

Description

The aim of the Element Timing API is to give web developers or analytics tools the ability to measure rendering timestamps of critical elements on a page.

The API supports timing information on the following elements:

• {{htmlelement("img")}}  elements,
• {{SVGElement("image")}}  elements inside an {{SVGElement("svg")}} ,
• poster images of {{htmlelement("video")}}  elements,
• elements which have a contentful {{cssxref("background-image")}}  property with a URL value for a resource that is actually available, and
• groups of text nodes, such as a {{htmlelement("p")}} .

The author flags an element for observation by adding the elementtiming attribute on the element.

PerformanceElementTiming inherits from {{domxref("PerformanceEntry")}} .

{{InheritanceDiagram}} 

Instance properties

This interface extends the following {{domxref("PerformanceEntry")}}  properties for event timing performance entry types by qualifying them as follows:

• {{domxref("PerformanceEntry.duration")}}  {{ReadOnlyInline}}  {{Experimental_Inline}} 
  • : Always returns 0 as duration does not apply to this interface.
• {{domxref("PerformanceEntry.entryType")}}  {{ReadOnlyInline}}  {{Experimental_Inline}} 
  • : Always returns "element".
• {{domxref("PerformanceEntry.name")}}  {{ReadOnlyInline}}  {{Experimental_Inline}} 
  • : Returns "image-paint" for images and "text-paint" for text.
• {{domxref("PerformanceEntry.startTime")}}  {{ReadOnlyInline}}  {{Experimental_Inline}} 
  • : Returns the value of this entry’s {{domxref("PerformanceElementTiming.renderTime", "renderTime")}}  if it is not 0, otherwise the value of this entry’s {{domxref("PerformanceElementTiming.loadTime", "loadTime")}} .

This interface also supports the following properties:

• {{domxref("PerformanceElementTiming.element")}}  {{ReadOnlyInline}}  {{Experimental_Inline}} 
  • : An {{domxref("Element")}}  representing the element we are returning information about.
• {{domxref("PerformanceElementTiming.id")}}  {{ReadOnlyInline}}  {{Experimental_Inline}} 
  • : A string which is the id of the element.
• {{domxref("PerformanceElementTiming.identifier")}}  {{ReadOnlyInline}}  {{Experimental_Inline}} 
  • : A string which is the value of the elementtiming attribute on the element.
• {{domxref("PerformanceElementTiming.intersectionRect")}}  {{ReadOnlyInline}}  {{Experimental_Inline}} 
  • : A {{domxref("DOMRectReadOnly")}}  which is the rectangle of the element within the viewport.
• {{domxref("PerformanceElementTiming.loadTime")}}  {{ReadOnlyInline}}  {{Experimental_Inline}} 
  • : A {{domxref("DOMHighResTimeStamp")}}  with the loadTime of the element.
• {{domxref("PerformanceElementTiming.naturalHeight")}}  {{ReadOnlyInline}}  {{Experimental_Inline}} 
  • : An unsigned 32-bit integer (unsigned long) which is the intrinsic height of the image if this is applied to an image, 0 for text.
• {{domxref("PerformanceElementTiming.naturalWidth")}}  {{ReadOnlyInline}}  {{Experimental_Inline}} 
  • : An unsigned 32-bit integer (unsigned long) which is the intrinsic width of the image if this is applied to an image, 0 for text.
• {{domxref("PerformanceElementTiming.renderTime")}}  {{ReadOnlyInline}}  {{Experimental_Inline}} 
  • : A {{domxref("DOMHighResTimeStamp")}}  with the renderTime of the element.
• {{domxref("PerformanceElementTiming.url")}}  {{ReadOnlyInline}}  {{Experimental_Inline}} 
  • : A string which is the initial URL of the resources request for images, 0 for text.

Instance methods

• {{domxref("PerformanceElementTiming.toJSON()")}}  {{Experimental_Inline}} 
  • : Returns a JSON representation of the PerformanceElementTiming object.

Examples

Observing render time of specific elements

In this example two elements are being observed by adding the elementtiming attribute. A {{domxref("PerformanceObserver")}}  is registered to get all performance entries of type "element" and the buffered flag is used to access data from before observer creation.

<img src="image.jpg" elementtiming="big-image" />
<p elementtiming="text" id="text-id">text here</p>

const observer = new PerformanceObserver((list) => {
  list.getEntries().forEach((entry) => {
    console.log(entry);
  });
});
observer.observe({ type: "element", buffered: true });

Two entries will be output to the console. The first containing details of the image, the second with details of the text node.

Specifications

{{Specifications}} 

Browser compatibility

{{Compat}} 

See also

• elementtiming HTML attribute