Usage in Deno
import * as mod from "node:v8";
The node:v8 module exposes APIs that are specific to the version of V8 built into the Node.js binary. It can be accessed using:
import v8 from 'node:v8';
A subclass of Deserializer corresponding to the format written by DefaultSerializer.
A subclass of Serializer that serializes TypedArray(in particular Buffer) and DataView objects as host objects, and onlystores the part of their underlying ArrayBuffers that they are referring to.
Returns an integer representing a version tag derived from the V8 version,command-line flags, and detected CPU features. This is useful for determiningwhether a vm.Script cachedData buffer is compatible with this instanceof V8.
Uses a DefaultDeserializer with default options to read a JS valuefrom a buffer.
Get statistics about code and its metadata in the heap, seeV8 GetHeapCodeAndMetadataStatistics API. Returns an object with thefollowing properties:
Generates a snapshot of the current V8 heap and returns a ReadableStream that may be used to read the JSON serialized representation.This JSON stream format is intended to be used with tools such asChrome DevTools. The JSON schema is undocumented and specific to theV8 engine. Therefore, the schema may change from one version of V8 to the next.
Returns statistics about the V8 heap spaces, i.e. the segments which make upthe V8 heap. Neither the ordering of heap spaces, nor the availability of aheap space can be guaranteed as the statistics are provided via theV8 GetHeapSpaceStatistics function and may change from one V8 version to thenext.
Returns an object with the following properties:
This is similar to the queryObjects() console APIprovided by the Chromium DevTools console. It can be used to search for objects that have the matching constructor on its prototype chainin the heap after a full garbage collection, which can be useful for memory leak regression tests. To avoid surprising results, users shouldavoid using this API on constructors whose implementation they don't control, or on constructors that can be invoked by other parties in theapplication.
Uses a DefaultSerializer to serialize value into a buffer.
The v8.setFlagsFromString() method can be used to programmatically setV8 command-line flags. This method should be used with care. Changing settingsafter the VM has started may result in unpredictable behavior, includingcrashes and data loss; or it may simply do nothing.
The API is a no-op if --heapsnapshot-near-heap-limit is already set from the command line or the API is called more than once.limit must be a positive integer. See --heapsnapshot-near-heap-limit for more information.
The v8.stopCoverage() method allows the user to stop the coverage collectionstarted by NODE_V8_COVERAGE, so that V8 can release the execution countrecords and optimize code. This can be used in conjunction with takeCoverage if the user wants to collect the coverage on demand.
The v8.takeCoverage() method allows the user to write the coverage started by NODE_V8_COVERAGE to disk on demand. This method can be invoked multipletimes during the lifetime of the process. Each time the execution counter willbe reset and a new coverage report will be written to the directory specifiedby NODE_V8_COVERAGE.
Generates a snapshot of the current V8 heap and writes it to a JSONfile. This file is intended to be used with tools such as ChromeDevTools. The JSON schema is undocumented and specific to the V8engine, and may change from one version of V8 to the next.
Called immediately after a promise continuation executes. This may be after a then(), catch(), or finally() handler or before an await after another await.
Called before a promise continuation executes. This can be in the form of then(), catch(), or finally() handlers or an await resuming.
Key events in the lifetime of a promise have been categorized into four areas: creation of a promise, before/after a continuation handler is called oraround an await, and when the promise resolves or rejects.
Called when a promise is constructed. This does not mean that corresponding before/after events will occur, only that the possibility exists. This willhappen if a promise is created without ever getting a continuation.
Called when the promise receives a resolution or rejection value. This may occur synchronously in the case of Promise.resolve() orPromise.reject().
The promiseHooks interface can be used to track promise lifecycle events.
The v8.startupSnapshot interface can be used to add serialization and deserialization hooks for custom startup snapshots.