PerformancePaintTiming: toJSON() method
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2021.
The toJSON() method of the PerformancePaintTiming interface returns a JSON-serializable plain object representing the PerformancePaintTiming object.
The method is automatically called by JSON.stringify() when a PerformancePaintTiming object is encountered during JSON serialization.
Syntax
toJSON()
Parameters
None.
Return value
A JSON-serializable plain object containing the following properties:
Each property's value is copied as-is.
Examples
Calling toJSON() directly
This example obtains a PerformancePaintTiming 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.name); // Same value as entry.name
});
});
observer.observe({ type: "paint", 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": "first-contentful-paint",
"entryType": "paint",
"startTime": 236.5,
"duration": 0,
"navigationId": 2463,
"paintTime": 230.25,
"presentationTime": 236.5
}
Specifications
| Specification |
|---|
| Paint Timing # dom-performancepainttiming-tojson |