PerformanceEntry

The PerformanceEntry object encapsulates a single performance metric that is part of the browser's performance timeline.

The Performance API offers built-in metrics which are specialized subclasses of PerformanceEntry. This includes entries for resource loading, event timing, first input delay (FID), and more.

A performance entry can also be created by calling the Performance.mark() or Performance.measure() methods at an explicit point in an application. This allows you to add your own metrics to the performance timeline.

The PerformanceEntry instances will always be one of the following subclasses:

• LargestContentfulPaint
• LayoutShift
• PerformanceEventTiming
• PerformanceLongAnimationFrameTiming
• PerformanceLongTaskTiming
• PerformanceMark
• PerformanceMeasure
• PerformanceNavigationTiming
• PerformancePaintTiming
• PerformanceResourceTiming
• PerformanceScriptTiming
• PerformanceServerTiming
• TaskAttributionTiming
• VisibilityStateEntry

PerformanceEntry.name Read only

A string representing the name for a performance entry. The value depends on the subtype.

PerformanceEntry.entryType Read only

A string representing the type of performance metric. For example, "mark" when PerformanceMark is used.

PerformanceEntry.startTime Read only

A DOMHighResTimeStamp representing the starting time for the performance metric.

PerformanceEntry.duration Read only

A DOMHighResTimeStamp representing the duration of the performance entry.

PerformanceEntry.toJSON()

Returns a JSON representation of the PerformanceEntry object.

The following example creates PerformanceEntry objects that are of the types PerformanceMark and PerformanceMeasure. The PerformanceMark and PerformanceMeasure subclasses inherit the duration, entryType, name, and startTime properties from PerformanceEntry and set them to their appropriate values.

// Place at a location in the code that starts login
performance.mark("login-started");

// Place at a location in the code that finishes login
performance.mark("login-finished");

// Measure login duration
performance.measure("login-duration", "login-started", "login-finished");

function perfObserver(list, observer) {
  list.getEntries().forEach((entry) => {
    if (entry.entryType === "mark") {
      console.log(`${entry.name}'s startTime: ${entry.startTime}`);
    }
    if (entry.entryType === "measure") {
      console.log(`${entry.name}'s duration: ${entry.duration}`);
    }
  });
}
const observer = new PerformanceObserver(perfObserver);
observer.observe({ entryTypes: ["measure", "mark"] });