The toJSON() method of the LayoutShiftAttribution interface is a serializer that returns a JSON representation of the LayoutShiftAttribution object.

None.

A JSON object that is the serialization of the LayoutShiftAttribution object.

The following example prints a JSON representation of the first item in LayoutShift.sources to the console.

new PerformanceObserver((list) => {
  for (const { sources } of list.getEntries()) {
    if (sources) {
      console.log(sources[0].toJSON());
    }
  }
}).observe({ type: "layout-shift", buffered: true });