PerformanceLongAnimationFrameTiming: toJSON() method
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The toJSON() method of the PerformanceLongAnimationFrameTiming interface returns a JSON-serializable plain object representing the PerformanceLongAnimationFrameTiming object.
The method is automatically called by JSON.stringify() when a PerformanceLongAnimationFrameTiming object is encountered during JSON serialization.
Syntax
toJSON()
Parameters
None.
Return value
A JSON-serializable plain object containing the following properties:
nameentryTypestartTimedurationnavigationIdpaintTimepresentationTimerenderStartstyleAndLayoutStartfirstUIEventTimestampblockingDurationscripts
Each property's value is copied as-is. When the returned object is passed to JSON.stringify(), the objects in the scripts array are further serialized using PerformanceScriptTiming.toJSON().
Examples
Calling toJSON() directly
This example obtains a PerformanceLongAnimationFrameTiming object. Calling toJSON() directly returns a plain object. Its properties have the same values as the corresponding properties of the original object.
const observer = new PerformanceObserver((list) => {
list.getEntries().forEach((entry) => {
const json = entry.toJSON();
console.log(json); // A plain object
console.log(typeof json); // "object"
console.log(json.blockingDuration); // Same value as entry.blockingDuration
});
});
observer.observe({ type: "long-animation-frame", buffered: true });
Serializing to a JSON string
Within the callback from the previous example, the same object can be serialized using JSON.stringify(), which calls the toJSON() method automatically.
console.log(JSON.stringify(entry));
This would log a JSON string like so (formatted for readability):
{
"name": "long-animation-frame",
"entryType": "long-animation-frame",
"startTime": 11802.25,
"duration": 60.5,
"navigationId": 2463,
"paintTime": 11862.75,
"presentationTime": 11868.5,
"renderStart": 11859.5,
"styleAndLayoutStart": 11859.5,
"firstUIEventTimestamp": 11801.25,
"blockingDuration": 2.5,
"scripts": [
{
"name": "script",
"entryType": "script",
"startTime": 11803.25,
"duration": 49.25,
"navigationId": 2463,
"invoker": "DOMWindow.onclick",
"invokerType": "event-listener",
"windowAttribution": "self",
"executionStart": 11803.25,
"forcedStyleAndLayoutDuration": 0.5,
"pauseDuration": 0.25,
"sourceURL": "https://web.dev/js/index-ffde4443.js",
"sourceFunctionName": "myClickHandler",
"sourceCharPosition": 17796
}
]
}
Specifications
| Specification |
|---|
| Long Animation Frames API # dom-performancelonganimationframetiming-tojson |