Performance API

High Resolution Time 規格は、アプリケーション内でクライアント側の待ち時間測定をサポートする Performance インターフェイスを定義しています。Performance インターフェイスは 1000 分の 1 ミリ秒の精度であるため、高解像度と見なされます (ハードウェアまたはソフトウェアの制約を受けます)。これらのインターフェイスは、フレームレートの計算 (アニメーションでは潜在的に重要) やベンチマーク (リソースのロード時間など) を含む、さまざまな使用例をサポートしています。

Since a platform's system clock is subject to various skews (such as NTP adjustments), the interfaces support a monotonic clock i.e. a clock that is always increasing. As such, the Performance API defines a DOMHighResTimeStamp type rather than using the Date.now() interface.

DOMHighResTimeStamp

The DOMHighResTimeStamp type, as its name implies, represents a high resolution point in time. This type is a double and is used by the performance interfaces. The value could be a discrete point in time or the difference in time between two discrete points in time.

The unit of DOMHighResTimeStamp is milliseconds and should be accurate to 5 µs (microseconds). However, If the browser is unable to provide a time value accurate to 5 microseconds (because, for example, due to hardware or software constraints), the browser can represent a the value as a time in milliseconds accurate to a millisecond.

メソッド

The Performance interface has two methods. The now() method returns a DOMHighResTimeStamp whose value that depends on the navigation start and scope. If the scope is a window, the value is the time the browser context was created and if the scope is a worker, the value is the time the worker was created.

The toJSON() method returns a serialization of the Performance object, for those attributes that can be serialized.

プロパティ

The Performance interface has two properties. The timing property returns a PerformanceTiming object containing latency-related performance information such as the start of navigation time, start and end times for redirects, start and end times for responses, etc.

The navigation property returns a PerformanceNavigation object representing the type of navigation that occurs in the given browsing context, such as the page was navigated to from history, the page was navigated to by following a link, etc.

インターフェイス

Performance
Provides methods and properties containing timing-related performance information for the given page.
PerformanceEntry
Provides methods and properties the encapsulate a single performance metric that is part of the performance timeline.
PerformanceFrameTiming
Provides methods and properties containing frame timing data about the browser's event loop.
PerformanceMark
An abstract interface for performance entries with an entry type of "mark". Entries of this type are created by calling performance.mark() to add a named DOMHighResTimeStamp (the mark) to the browser's performance timeline.
PerformanceMeasure
An abstract interface for performance entries with an entry type of "measure". Entries of this type are created by calling performance.measure() to add a namedDOMHighResTimeStamp (the measure) between two marks to the browser's performance timeline.
PerformanceNavigationTiming
Provides methods and properties to store and retrieve high resolution timestamps or metrics regarding the browser's document navigation events. 
PerformanceObserver
Provides methods and properties used to observe performance measurement events and be notified of new performance entries as they are recorded in the browser's performance timeline.
PerformanceResourceTiming
Provides methods and properties for retrieving and analyzing detailed network timing data regarding the loading of an application's resources.

仕様

仕様書 ステータス コメント
High Resolution Time 勧告 Initial definition.
High Resolution Time Level 2 勧告候補 Adds performance attribute on Window and WorkerGlobalScope.
High Resolution Time Level 3 編集者草案 Add timeOrigin property to Performance interface.
Frame Timing ドラフト Adds PerformanceFrameTiming interface.
Navigation Timing 勧告 Adds the PerformanceTiming and PerformanceNavigation interfaces. Adds timing and navigation properties to the Performance interface.
Navigation Timing Level 2 草案 Adds the PerformanceNavigationTiming interface. Obsolete's the the PerformanceTiming interface, the PerformanceNavigation interface, as well as the timing and navigation properties to the Performance interface.
Performance Timeline 勧告 Adds the PerformanceEntry interface, the PerformanceEntryList type, as well as the getEntries(), getEntriesByType(), and getEntriesByName() methods on the Performance interface.
Performance Timeline Level 2 勧告候補 Adds serializer to the PerformanceEntry interface as well as adding the PerformanceObserver interface and callback
Resource Timing Level 1 勧告候補 Adds the PerformanceResourceTiming interface. Adds the clearResourceTimings() method, the setResourceTimingBufferSize() method, and the onresourcetimingbufferfull event handler to the Performance interface. Also adds the Timing-Allow-Origin response header.
Resource Timing Level 2 草案 Adds the nextHopProtocol, workerStart, transferSize, encodedBodySize, and decodedBodySize properties to the PerformanceResourceTiming interface. 
Resource Timing Level 3 編集者草案  
User Timing 勧告 Adds mark(), clearMarks(), measure() and clearMeasures() methods to the Performance interface. Adds the PerformanceMark and PeformanceMeasure interfaces.
User Timing Level 2 草案  

実装状況

As shown in the Performance interface's Browser Compatibility table, most of these interfaces are broadly implemented by desktop browsers.

To test your browser's support for the Performance interface, run the perf-api-support application.

あわせて参照