PerformancePaintTiming - Web APIs 编辑

The PerformancePaintTiming interface of the Paint Timing API provides timing information about "paint" (also called "render") operations during web page construction. "Paint" refers to conversion of the render tree to on-screen pixels.

An application can register a PerformanceObserver for "paint" performance entry types and the observer can retrieve the times that paint events occur. Use this information to help identify areas that take too long to provide a good user experience.

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Properties

This interface has no properties but it extends the following PerformanceEntry properties (for "paint" performance entry types) by qualifying and constraining the properties as follows:

PerformanceEntry.entryType

Returns "paint".

PerformanceEntry.name

Returns either "first-paint" or "first-contentful-paint".

PerformanceEntry.startTime

Returns the timestamp when the paint occurred.

PerformanceEntry.duration

Returns 0.

Methods

This interface has no methods.

Example

function showPaintTimings() {
  if (window.performance) {
    let performance = window.performance;
    let performanceEntries = performance.getEntriesByType('paint');
    performanceEntries.forEach( (performanceEntry, i, entries) => {
      console.log("The time to " + performanceEntry.name + " was " + performanceEntry.startTime + " milliseconds.");
    });
  } else {
    console.log('Performance timing isn\'t supported.');
  }
}

The code above produces console output something like the following:

The time to first-paint was 2785.915 milliseconds.
The time to first-contentful-paint was 2787.460 milliseconds.

Specifications

Browser compatibility

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