Performance API - Web APIs 编辑
The High Resolution Time standard defines a Performance interface that supports client-side latency measurements within applications. The Performance interfaces are considered high resolution because they are accurate to a thousandth of a millisecond (subject to hardware or software constraints). The interfaces support a number of use cases including calculating frame-rates (potentially important in animations) and benchmarking (such as the time to load a resource).
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 the value as a time in milliseconds accurate to a millisecond.
Methods
The Performancenow() 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.
Properties
The Performancetiming 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 navigationPerformanceNavigation 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.
Interfaces
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 entrieswith anentry typeof "mark". Entries of this type are created by callingperformance.mark()to add a namedDOMHighResTimeStamp(the mark) to the browser's performance timeline. PerformanceMeasure- An abstract interface for
performance entrieswith anentry typeof "measure". Entries of this type are created by callingperformance.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 timestampsor 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.
Specifications
| Specification | Status | Comment |
|---|---|---|
| High Resolution Time | Recommendation | Initial definition. |
| High Resolution Time Level 2 | Recommendation | Adds performance attribute on Window and WorkerGlobalScope. |
| High Resolution Time Level 3 | Editor's Draft | Add timeOrigin property to Performance interface. |
| Frame Timing | Draft | Adds PerformanceFrameTiming interface. |
| Navigation Timing | Recommendation | Adds the PerformanceTiming and PerformanceNavigation interfaces. Adds timing and navigation properties to the Performance interface. |
| Navigation Timing Level 2 | Working Draft | Adds the PerformanceNavigationTiming interface. Obsolete's the PerformanceTiming interface, the PerformanceNavigation interface, as well as the timing and navigation properties to the Performance interface. |
| Performance Timeline | Recommendation | Adds the PerformanceEntry interface, the PerformanceEntryList type, as well as the getEntries(), getEntriesByType(), and getEntriesByName() methods on the Performance interface. |
| Performance Timeline Level 2 | Candidate Recommendation | Adds serializer to the PerformanceEntry interface as well as adding the PerformanceObserver interface and callback |
| Resource Timing Level 1 | Candidate Recommendation | 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 | Working Draft | Adds the nextHopProtocol, workerStart, transferSize, encodedBodySize, and decodedBodySize properties to the PerformanceResourceTiming interface. |
| Resource Timing Level 3 | Editor's Draft | |
| User Timing | Recommendation | Adds mark(), clearMarks(), measure() and clearMeasures() methods to the Performance interface. Adds the PerformanceMark and PeformanceMeasure interfaces. |
| User Timing Level 2 | Working Draft |
Implementation status
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.
See also
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