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Performance - Web APIs 编辑

The Performance interface provides access to performance-related information for the current page. It's part of the High Resolution Time API, but is enhanced by the Performance Timeline API, the Navigation Timing API, the User Timing API, and the Resource Timing API.

An object of this type can be obtained by calling the window.performance read-only attribute.

Note: This interface and its members are available in Web Workers via WorkerGlobalScope.performance , except where indicated below. Also, note that performance markers and measures are per context. If you create a mark on the main thread (or other worker), you cannot see it in a worker thread, and vice versa.

Properties

The Performance interface doesn't inherit any properties.

Performance.navigation Read only: A legacy PerformanceNavigation object that provides useful context about the operations included in the times listed in timing, including whether the page was a load or a refresh, how many redirections occurred, and so forth.
Not available in workers.
Performance.timing Read only: A legacy PerformanceTiming object containing latency-related performance information.
Not available in workers.
Performance.memory Read only: A non-standard extension added in Chrome, this property provides an object with basic memory usage information. You should not use this non-standard API.
Performance.timeOrigin Read only: Returns the high resolution timestamp of the start time of the performance measurement.

Methods

The Performance interface doesn't inherit any methods.

Performance.clearMarks(): Removes the given mark from the browser's performance entry buffer.
Performance.clearMeasures(): Removes the given measure from the browser's performance entry buffer.
Performance.clearResourceTimings(): Removes all performance entries with a entryType of "resource" from the browser's performance data buffer.
Performance.getEntries(): Returns a list of PerformanceEntry objects based on the given filter.
Performance.getEntriesByName(): Returns a list of PerformanceEntry objects based on the given name and entry type.
Performance.getEntriesByType(): Returns a list of PerformanceEntry objects of the given entry type.
Performance.mark(): Creates a timestamp in the browser's performance entry buffer with the given name.
Performance.measure(): Creates a named timestamp in the browser's performance entry buffer between two specified marks (known as the start mark and end mark, respectively).
Performance.now(): Returns a DOMHighResTimeStamp representing the number of milliseconds elapsed since a reference instant.
Performance.setResourceTimingBufferSize(): Sets the browser's resource timing buffer size to the specified number of "resource" type performance entry objects.
Performance.toJSON(): Is a jsonizer returning a json object representing the Performance object.

Events

Listen to these events using addEventListener() or by assigning an event listener to the oneventname property of this interface.

resourcetimingbufferfull: Fired when the browser's resource timing buffer is full.
Also available via the onresourcetimingbufferfull property.

Specifications

Specification	Status	Comment
High Resolution Time Level 2 The definition of 'Performance' in that specification.	Recommendation	Defines `toJson()` method.
High Resolution Time The definition of 'Performance' in that specification.	Recommendation	Defines `now()` method.
Performance Timeline Level 2 The definition of 'Performance extensions' in that specification.	Candidate Recommendation	Changes `getEntries()` interface.
Performance Timeline The definition of 'Performance extensions' in that specification.	Recommendation	Defines `getEntries()`, `getEntriesByType()` and `getEntriesByName()` methods.
Resource Timing Level 1 The definition of 'Performance extensions' in that specification.	Candidate Recommendation	Defines `clearResourceTimings()` and `setResourceTimingBufferSize()` methods and the `onresourcetimingbufferfull` property.
User Timing Level 2 The definition of 'Performance extensions' in that specification.	Working Draft	Clarifies `mark()`, `clearMark()`, `measure()` and `clearMeasure()` methods.
User Timing The definition of 'Performance extensions' in that specification.	Recommendation	Defines `mark()`, `clearMark()`, `measure()` and `clearMeasure()` methods.