PerformanceEventTiming: interactionId property

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

The read-only interactionId property of the PerformanceEventTiming interface returns an ID that uniquely identifies a user interaction which triggered a series of associated events.

Value

A number. For event types where an interaction ID is not calculated the value is 0.

When a user interacts with a web page, a user interaction (for example a click) usually triggers a sequence of events, such as pointerdown, pointerup, and click events. To measure the latency of this series of events, the events share the same interactionId.

An interactionId is only computed for the following event types belonging to a user interaction. It is 0 otherwise.

Event types	User interaction
`pointerdown`, `pointerup`, `click`	click / tap / drag
`keydown`, `keyup`	key press

The interactionId is also needed to calculate the Interaction to next paint metric, which helps analyze responsiveness to user interaction over the lifetime of a page.

Examples

Using interactionId

The following example collects event duration for all events corresponding to an interaction. The eventLatencies map can then be used to find events with maximum duration for a user interaction, for example.

// The key is the interaction ID.
let eventLatencies = {};

const observer = new PerformanceObserver((list) => {
  list.getEntries().forEach((entry) => {
    if (entry.interactionId > 0) {
      const interactionId = entry.interactionId;
      if (!eventLatencies.has(interactionId)) {
        eventLatencies[interactionId] = [];
      }
      eventLatencies[interactionId].push(entry.duration);
    }
  });
});

observer.observe({ type: "event", buffered: true });

// Log events with maximum event duration for a user interaction
Object.entries(eventLatencies).forEach(([k, v]) => {
  console.log(Math.max(...v));
});