# node:perf_hooks

> How Elide supports Node's `perf_hooks`: it shares one timeline with the Web performance globals; `constants` is empty and resource timing is absent.

`node:perf_hooks` follows [Node's `perf_hooks`](https://nodejs.org/api/perf_hooks.html); its `performance` and
constructors are the same objects as the [Performance globals](https://elide.help/docs/api-wintercg-performance).

## Example

```js
// perf.mjs
import { PerformanceObserver, performance } from "node:perf_hooks";

const observer = new PerformanceObserver((list) => {
  for (const entry of list.getEntries()) console.log(entry.entryType, entry.name, entry.duration >= 0);
  observer.disconnect();
});
observer.observe({ entryTypes: ["measure"] });

performance.mark("start");
for (let i = 0; i < 1e5; i++);
performance.mark("end");
performance.measure("loop", "start", "end");
console.log(performance.getEntriesByType("mark").map((mark) => mark.name).join());
```

`elide run perf.mjs` prints:

```text
start,end
measure loop true
```

## Differences from Node

- `constants` is an empty object.
- `PerformanceResourceTiming` is absent.
- `nodeTiming.v8Start`, `environment`, `loopExit`, and `idleTime` are zero.

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## Reference

**Status:** Partial · Not measured · since 1.1.0

### Exports

| Export | Kind | Status | Notes |
| --- | --- | --- | --- |
| `PerformanceEntry` | class | Full | `name`, `entryType`, `startTime`, `duration`, `detail`, `toJSON()` |
| `PerformanceMark` | class | Full |  |
| `PerformanceMeasure` | class | Full |  |
| `PerformanceNodeTiming` | class | Full | `nodeStart`, `v8Start`, `environment`, `bootstrapComplete`, `loopStart`, `loopExit`, `idleTime` |
| `PerformanceObserverEntryList` | class | Full | `getEntries()`, `getEntriesByName()`, `getEntriesByType()` |
| `PerformanceObserver` | class | Full | `observe()`, `disconnect()`, `takeRecords()`, `PerformanceObserver.supportedEntryTypes` |
| `now()` | function | Full | Returns the current high-resolution millisecond timestamp relative to timeOrigin |
| `mark()` | function | Full | Creates a performance mark with the given name |
| `measure()` | function | Full | Creates a performance measure between two marks or timestamps |
| `getEntries()` | function | Full | Returns a list of all performance entries |
| `getEntriesByName()` | function | Full | Returns performance entries filtered by name |
| `getEntriesByType()` | function | Full | Returns performance entries filtered by type ("mark" or "measure") |
| `clearMarks()` | function | Full | Removes all marks, or only marks with the given name |
| `clearMeasures()` | function | Full | Removes all measures, or only measures with the given name |
| `timeOrigin` | property | Full | The high-resolution millisecond timestamp at which the process started |
| `nodeTiming` | property | Full | Timing information about the Node.js process lifecycle |

### Not implemented

`Performance`, `PerformanceResourceTiming`.
<!-- api-reference:end -->