PerformanceScriptTiming
Limited availability
This feature is not Baseline because it does not work in some of the most widely-used browsers.
Experimental:This is anexperimental technology
Check theBrowser compatibility table carefully before using this in production.
ThePerformanceScriptTiming interface is specified in the Long Animation Frames API and provides metrics on individual scripts that contribute to long animation frames (LoAFs).
Description
Long animation frames (LoAFs) are rendering updates that are delayed beyond 50ms. LoAFs can result in slow user interface (UI) updates, making controls appear unresponsive and causingjanky (non-smooth) animated effects and scrolling. This often leads to user frustration.
ThePerformanceScriptTiming interface (instances of which are accessed via thePerformanceLongAnimationFrameTiming.scripts property) provides the following granular set of information on individual scripts that contribute to LoAFs, allowing developers to narrow down their root causes:
- A detailed set of timestamps for each script.
- The identity and type of the invoker, i.e., the feature that, when invoked, ran the script.
- Detailed information on each script source file, including the URL, and the function name and character position that contributed to the LoAF.
PerformanceScriptTiming inherits fromPerformanceEntry.
Instance properties
This interface extends the followingPerformanceEntry properties for long animation frame performance entries:
PerformanceEntry.durationRead onlyExperimentalReturns a
DOMHighResTimeStamprepresenting the elapsed time in milliseconds between the start and end of the script's execution.PerformanceEntry.entryTypeRead onlyExperimentalReturns the entry type, which is always
"script".PerformanceEntry.nameRead onlyExperimentalReturns the entry name, which is always
"script".PerformanceEntry.startTimeRead onlyExperimentalReturns a
DOMHighResTimeStamprepresenting the time when the script execution started, in milliseconds.
This interface also supports the following properties:
PerformanceScriptTiming.executionStartRead onlyExperimentalReturns a
DOMHighResTimeStampindicating the time when the script compilation finished and execution started.PerformanceScriptTiming.forcedStyleAndLayoutDurationRead onlyExperimentalReturns a
DOMHighResTimeStampindicating the total time spent, in milliseconds, by the script processing forced layout/style. SeeAvoid layout thrashing to understand what causes this.PerformanceScriptTiming.invokerRead onlyExperimentalReturns a string value indicating the identity of the feature that, when invoked, ran the script.
PerformanceScriptTiming.invokerTypeRead onlyExperimentalReturns a string value indicating the type of feature that, when invoked, ran the script.
PerformanceScriptTiming.pauseDurationRead onlyExperimentalReturns a
DOMHighResTimeStampindicating the total time, in milliseconds, spent by the script on "pausing" synchronous operations (for example,Window.alert()calls or synchronousXMLHttpRequests).PerformanceScriptTiming.sourceCharPositionRead onlyExperimentalReturns a number representing the script character position of the script feature that contributed to the LoAF.
PerformanceScriptTiming.sourceFunctionNameRead onlyExperimentalReturns a string representing the name of the function that contributed to the LoAF.
PerformanceScriptTiming.sourceURLRead onlyExperimentalReturns a string representing the URL of the script.
PerformanceScriptTiming.windowRead onlyExperimentalReturns a reference to a
Windowobject representing thewindowof the container (i.e., either the top-level document or an<iframe>) in which the LoAF-causing script was executed.PerformanceScriptTiming.windowAttributionRead onlyExperimentalReturns an enumerated value describing the relationship of the container (i.e., either the top-level document or an
<iframe>) in which the LoAF-causing script was executed, relative to the window running the current document.
Instance methods
PerformanceScriptTiming.toJSON()ExperimentalReturns a JSON representation of the
PerformanceScriptTimingobject.
Examples
SeeLong animation frame timing for examples related to the Long Animation Frames API.
Specifications
| Specification |
|---|
| Long Animation Frames API # sec-PerformanceScriptTiming |