LayoutShift: lastInputTime property

The lastInputTime read-only property of the LayoutShift interface returns the time of the most recent excluding input or 0 if no excluding input has occurred.

Layout shifts are only bad if the user wasn't expecting them. Many layout shift metrics (like Cumulative Layout Shift (CLS)) exclude shifts that occurred soon after certain user interactions. These interactions are called excluding inputs. Excluding inputs are:

• Any events which signal a user's active interaction with the document: (mousedown, keydown, and pointerdown)
• Any events which directly changes the size of the viewport.
• change events.

The mousemove and pointermove events are not excluding inputs.

const observer = new PerformanceObserver((list) => {
  list.getEntries().forEach((entry) => {
    if (entry.lastInputTime) {
      console.log(entry.lastInputTime);
    }
  });
});

observer.observe({ type: "layout-shift", buffered: true });