node:v8

node:v8 exports six members of Node’s v8.

Example

// v8.mjs
import v8 from "node:v8";

const bytes = v8.serialize({ id: 7, tags: ["a"] });
console.log(JSON.stringify(v8.deserialize(bytes)));
const heap = v8.getHeapStatistics();
console.log(heap.used_heap_size > 0, heap.total_heap_size >= heap.used_heap_size);
console.log(typeof v8.cachedDataVersionTag());

utf-8 · js · Lines: 8

elide run v8.mjs prints:

text

{"id":7,"tags":["a"]}
true true
number

utf-8 · text · Lines: 3

Differences from Node

Only these members are exported:

Operation	Behavior
`cachedDataVersionTag()`	Returns a stable 32-bit tag for the running binary.
`getHeapStatistics()`	Returns a heap-statistics object in Node’s format.
`getHeapSpaceStatistics()`	Returns one entry per memory pool, with names such as `eden space`.
`setFlagsFromString(flags)`	Accepts a string and has no effect.
`serialize(value)`	Encodes `JSON.stringify(value)` as UTF-8 in a `Uint8Array`.
`deserialize(buffer)`	Decodes UTF-8 and parses the JSON.

serialize output is not V8’s structured-clone format; circular objects throw TypeError.

Reference

Status: Partial · Not measured · since 1.1.0

Exports

Export	Kind	Status	Notes
`getHeapStatistics()`	function	Full	Returns an object with V8 heap statistics
`getHeapSpaceStatistics()`	function	Full	Returns statistics about V8 heap spaces
`setFlagsFromString()`	function	Full	Set additional V8 command-line flags
`serialize()`	function	Full	Serializes a value into a buffer
`deserialize()`	function	Full	Reads a value written by serialize() from a buffer

Not implemented

DefaultDeserializer, DefaultSerializer, Deserializer, GCProfiler, Serializer, getCppHeapStatistics, getHeapCodeStatistics, getHeapSnapshot, isStringOneByteRepresentation, promiseHooks, queryObjects, setHeapSnapshotNearHeapLimit, startCpuProfile, startHeapProfile, startupSnapshot, stopCoverage, takeCoverage, writeHeapSnapshot.