PerformanceServerTiming: 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 March 2023.
Note: This feature is available in Web Workers.
The toJSON() method of the PerformanceServerTiming interface is a serializer; it returns a JSON representation of the PerformanceServerTiming object.
Syntax
toJSON()
Parameters
None.
Return value
A JSON object that is the serialization of the PerformanceServerTiming object.
Examples
Logging server timing entries
Server timing metrics require the server to send the Server-Timing header. For example:
Server-Timing: cache;desc="Cache Read";dur=23.2
The serverTiming entries can live on navigation and resource entries.
Example using a PerformanceObserver, which notifies of new navigation and resource performance entries as they are recorded in the browser's performance timeline. Use the buffered option to access entries from before the observer creation.
const observer = new PerformanceObserver((list) => {
list.getEntries().forEach((entry) => {
entry.serverTiming.forEach((serverEntry) => {
console.log(serverEntry.toJSON());
});
});
});
["navigation", "resource"].forEach((type) =>
observer.observe({ type, buffered: true }),
);
This would log a JSON object like so:
{
"name": "cache",
"duration": 23.2,
"description": "Cache Read"
}
To get a JSON string, you can use JSON.stringify(serverEntry) directly; it will call toJSON() automatically.
Specifications
| Specification |
|---|
| Server Timing # dom-performanceservertiming-tojson |
Browser compatibility
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