PerformanceEventTiming: processingStart property

The read-only processingStart property returns the time at which event dispatch started. This is when event handlers are about to be executed.


A DOMHighResTimeStamp timestamp.


Using the processingStart property

The processingStart property can be used when observing event timing entries (PerformanceEventTiming). For example, to calculate input delay or event processing times.

const observer = new PerformanceObserver((list) => {
  list.getEntries().forEach((entry) => {
    // Full duration
    const duration = entry.duration;
    // Input delay (before processing event)
    const delay = entry.processingStart - entry.startTime;
    // Synchronous event processing time
    // (between start and end dispatch)
    const time = entry.processingEnd - entry.processingStart;
// Register the observer for events
observer.observe({ type: "event", buffered: true });


Event Timing API
# dom-performanceeventtiming-processingstart

Browser compatibility

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See also