wasm-rquickjs

Introduction

Command line tool and library to generate a Rust crate wrapping JavaScript code into a WebAssembly Component using the QuickJS engine.

Generated components use QuickJS-ng 0.16.2 through rquickjs 0.14.0, including Unicode v-flag regular expression sets, intersections and subtraction.

The engine automatically collects unreachable reference cycles. Each runtime starts with a 32 MiB GC threshold, which the engine then adapts to its retained heap. Collection makes freed space reusable; WebAssembly linear memory keeps its high-water size. Explicit gc() remains optional and schedules collection after the current JavaScript execution completes.

Disposal uses the engine's well-known Symbol.dispose and Symbol.asyncDispose, including for generated WIT resources. These symbols are not in the global symbol registry, unlike Node.js 22.14. Their properties are read-only in both runtimes.

Comparison with ComponentizeJS

ComponentizeJS achieves the same goal of wrapping JavaScript code into a WebAssembly Component, but it does it using a modified version of the SpiderMonkey engine.

Advantages of wasm-rquickjs over ComponentizeJS:

At the time of writing, there are known bugs in ComponentizeJS (or one of its underlying modules) that prevents it from being used in production.
Much simpler to develop and debug, as everything exposed for JavaScript is implemented in async Rust using the rquickjs library
The WIT-JS mapping rules and the set of available JavaScript APIs are well defined
Smaller WASM binary size

Advantages of ComponentizeJS over wasm-rquickjs:

Faster runtime (due to the SpiderMonkey engine)
Faster startup time (it does pre-initialization with Wizer)
No need for the Rust toolchain for end users

Comparison with wasmedge-quickjs

The project is similar to wasmedge-quickjs in using te QuickJS engine compiled to WASM to run JavaScript code, but it is different in the following ways:

It does not provide support for using the component model from JS (defining imports and exports using WIT)
The imports the resulting WASM component has are WasmEdge specific

Usage

The tool can be used as a command line tool or as a library. The command line tool has two top level commands:

  generate-wrapper-crate  Generate the wrapper crate for a JavaScript module
  generate-dts            Generate TypeScript module definitions

Generating the wrapper crate

This is the primary command that generates the Rust crate embedding the JavaScript code into a WebAssembly Component.

Usage: wasm-rquickjs generate-wrapper-crate --js <JS> --wit <WIT> --output <OUTPUT>

The --js arguments is the path to the JavaScript file to be wrapped. There can be only one JavaScript file, containing an ES6 module exporting the necessary functions and classes as described below.
The --wit argument is the path to the WIT root containing a single world that describes the imports and exports of the component
The --output argument is the path to the output directory where the generated Rust crate will be created.

The output directory is going to contain a self-contained Rust crate that can be compiled into a WASM component using cargo build --target wasm32-wasip2.

Every generated crate also contains a target-specific THIRD_PARTY_COMPONENT_LICENSES.txt for the locked Cargo dependency union of the standard normal / normal-p3 TypeScript runtime and transform profiles. It is deliberately a superset for crates that enable fewer features. Distributors must ship that notice with the compiled component and separately audit application code, custom feature combinations, bundled JavaScript in the skeleton (including third-party code adapted from Node.js, Deno, and web-streams-polyfill), toolchain and WASI sysroot components, vendored native sources, and upstream NOTICE obligations. Maintainers can regenerate and verify the retained notices with tools/check-component-licenses.sh --write and --check, respectively, using the pinned cargo-about version named by the script.

The generated crate has some features that control what imports the component will have beside the ones defined in the user's WIT world:

logging: enables the wasi:logging import to be used for the JavaScript console API
http: enables the wasi:http import to be used for the JavaScript fetch API
sqlite: enables the node:sqlite module with an embedded SQLite database engine

By default logging and http are enabled. The sqlite feature must be explicitly enabled.

Choosing the WASI target

The --target option selects which WASI generation mode is used:

--target wasi-p2 (default): the historical WASI Preview 2 mode. Component exports are synchronous WIT functions and the full Node.js-compatible builtin set is available. This is the stable, production path.
--target wasi-p3: the opt-in WASI Preview 3 mode. WIT async func exports and imports use the Component Model async ABI, while plain functions remain synchronous. WIT future<T> / stream<T> values are supported at function boundaries, including inside composite types. See WASI Preview 3 target below for the current status and limitations.

Both targets generate a crate that is still compiled with cargo build --target wasm32-wasip2 (a dedicated wasm32-wasip3 rustc target does not exist yet; the Preview 3 crate uses the wasip3 bindings on top of the Preview 2 target).

Native modules and dependencies

A host application can give JavaScript its own Rust modules without editing the generated crate:

wasm-rquickjs generate-wrapper-crate ... \
  --native-module my-native=my_native::Module \
  --dependency 'my-native={ path = "../my-native" }'

--native-module <name>=<rust path> registers a type implementing rquickjs::module::ModuleDef so that JavaScript can import ... from '<name>'. The name must not be a JavaScript module name, an imported WIT interface, or in the reserved node: and __wasm_rquickjs_builtin/ namespaces. Like an embedded JavaScript module, a native module named after a schemeless builtin alias, such as fs, takes precedence over the alias for the component's own modules; node:fs still resolves to the builtin.
--dependency <key>=<TOML value> adds a [dependencies] entry, a version string or an inline table, and replaces an entry of the skeleton with the same key as a whole. A relative path is resolved against the current directory and written relative to the generated crate. With any --dependency, the skeleton's Cargo.lock is not copied: it was resolved for the unmodified dependencies. A fresh output directory then has no lock and Cargo resolves one on the first build; a Cargo.lock already in the output directory is kept.

Both options can be repeated and work with both targets. The native module's crate must use the same rquickjs version as the generated crate; the crate's [patch.crates-io] applies to it.

Generating TypeScript module definitions

The generate-dts command generates TypeScript module definitions for all the exported and imported interfaces:

Usage: wasm-rquickjs generate-dts --wit <WIT> --output <OUTPUT>

The --wit argument is the path to the WIT root containing a single world that describes the imports and exports of the component.
The --output argument is the path to the output directory where the generated TypeScript module definitions ( .d.ts) will be created.

Using with Golem

wasm-rquickjs is integrated into Golem's command line interface, so it can be directly used using Golem app templates.

Note: Golem's Preview 3 SDK/template builds pin the wasi-p3 generator branch and pass --target wasi-p3 when building their JavaScript guest images. Preview 2 remains the default for callers that do not select a target explicitly.

WASI Preview 3 target

Passing --target wasi-p3 to generate-wrapper-crate selects the opt-in, asynchronous WASI Preview 3 generation mode. It is intended for hosts that support the Component Model async ABI.

How it differs from Preview 2:

WIT async func exports and imports use the Component Model async ABI (task.return); plain functions remain synchronous.
The JavaScript event loop is driven by the Component Model async executor instead of Preview 2 wasi:io/poll pollables — there are no wstd/wasip2/pollable dependencies in the Preview 3 code path.
WIT future<T> and stream<T> are mapped to JavaScript Promise<T> and AsyncIterable<T> respectively, both directly and when nested in composite parameter/result types.
fetch / HTTP uses the wasi:http Preview 3 (wasi:http/handler) async client.

Building and running:

The generated crate is still built with cargo build --target wasm32-wasip2. Running the resulting component requires a host with Preview 3 and Component Model async support. For example, with the wasmtime CLI (version 46.x):

wasmtime run -S p3=y -S http=y --wasm component-model=y --wasm component-model-async=y \
  --invoke 'my-export()' path/to/component.wasm

The Node.js-compatible builtin set is available on Preview 3 as well. Working end-to-end examples live under examples/p3, covering async exports/imports, future<T>/stream<T> values, exported resources, and HTTP fetch.

Current limitations (Preview 3):

Composition (--js-modules name=@composition) is not supported yet.
An exported result containing future<T> or stream<T> must come from an async func; a synchronous export cannot return its reader before a backpressured writer starts.
The error arm of an exported top-level result<T, E> cannot contain future<T> or stream<T>.

Wizer pre-initialization (optimize) supports Preview 3 components. As with Preview 2, module initialization must become quiescent before the snapshot and cannot leave timers or tasks pending. Runtime arguments and environment variables are restored before the first export runs; modules must not capture their values or immutable aliases during top-level initialization.

External I/O during pre-initialization is rejected. Top-level filesystem probes (including existsSync and module/package lookup), socket/DNS/HTTP/WebSocket acquisition, SQLite opens (including :memory:), execution-job creation, and process.chdir() fail the build immediately. Catching a JavaScript exception cannot suppress this failure. The diagnostic identifies the operation and recommends moving it into an exported function or lazy initialization after restoration. This avoids saving unavailable build-time capabilities or false filesystem results in the snapshot. The optimizer also traps filesystem preopens, network acquisition and outgoing HTTP for older templates and custom initializers. Rebuild templates to get native guards, restore-safe pre-init stdio and guest diagnostics.

Importing these builtins, embedded/data modules and explicitly supplied module sources remains supported. Logging and pure computation remain available. process.cwd() is the logical / during pre-initialization and refreshes from the runtime environment after restoration. wasm-rquickjs:execution may be imported, but runJavaScript() and startJavaScript() are runtime-only, including for pure computation. Create jobs from an exported function or lazy runtime initialization. On cold start and after restoration, the main runtime honors wasi:cli/environment's initial cwd. Hosts must implement this standard WASI import; none retains /. A supplied cwd must be an accessible directory, or runtime initialization fails. Owned jobs retain their separate cwd.

Supplied CommonJS reexports that require filesystem analysis are still rejected during pre-initialization, even if a loader could supply the child at runtime. Defer those chains to runtime until loader-aware reexport analysis is supported. Defer SQLite connections with new DatabaseSync(path, { open: false }), then call .open() after restoration. Applications that require top-level external I/O should skip optimize and initialize at runtime instead.

Host exception diagnostics recognize native Errors and legacy Error-prototype objects and use bounded native stack frames without invoking application getters, coercion, toJSON, or Error.prepareStackTrace. Ordinary records and arrays show own data with a two-level depth limit, a shared 16-property budget and a 4096-byte summary limit; accessors, cycles and omitted entries are marked explicitly. Proxies and exotic objects remain opaque. Array inspection reads only a bounded prefix, while native record key discovery allocates a native table per visited record and may sort integer keys. Its cost grows with record size, including repeated visits to shared records; allocation failure falls back to an unavailable marker. Oversized strings receive bounded descriptions. When the engine supplies no usable position, the diagnostic explicitly says that the source location is unavailable. Existing source maps and wrapper offsets are read through guarded data lookup; unsafe, missing or overly expensive mappings fall back to generated code locations. Previously prepared stack text is reused within the same bounds without running its hook again. Readable bundles and source map configuration remain the responsibility of the build tooling. Public JavaScript .stack and prepareStackTrace behavior is unchanged.

Deterministic pre-initialization: newly generated P2 and P3 templates export wasm-rquickjs-wizer-restore-v1. When optimizing their wizer-initialize export, the optimizer supplies fixed-seed entropy, Unix-epoch wall time, and a zero monotonic clock, with empty arguments/environment. These services exist only in the optimizer store. Before any restored application JS runs, the guest reseeds its crypto RNG from runtime host entropy (failure traps) and refreshes its performance/uptime origin. Captured Math.random functions, including functions from node:vm contexts, use that reseeded RNG. Runtime clock reads still use the deployment host. Determinism is for identical input with the same optimizer and dependencies, not a cross-version artifact format guarantee. Initialization must also avoid external I/O and application-owned sources of nondeterminism; the optimizer does not make arbitrary application code reproducible.

Application initialization is still snapshotted. Values already computed at module top level—timestamps, random IDs, keys, library-owned PRNG state, performance marks, and copies of environment values—remain frozen. Internal-service refresh cannot undo those computations. Generate secrets and per-instance IDs after restoration, inside an exported function; do not generate them at module top level. Initialization must not depend on clocks advancing. Applications that need live top-level entropy/time should skip optimize and initialize at runtime instead.

Old/unmarked components and other initializer names retain legacy real entropy and clocks, with a warning: output is not guaranteed reproducible, and cached RNG state may still be shared by restored instances. Update both the optimizer and rebuild guest templates to enable the deterministic path safely. Updating the optimizer alone does not repair a published template or existing snapshots. The capability export is a template producer's declaration of this restore contract, not a guarantee that arbitrary application state or composed code is snapshot-safe.

Library callers using the optimize feature can configure the guest-to-host copy budget for initialization and Wizer snapshot memory extraction:

use wasm_rquickjs::{OptimizeOptions, optimize_component_with_options};

# async fn example(input: &camino::Utf8Path, output: &camino::Utf8Path) -> anyhow::Result<()> {
optimize_component_with_options(
    input,
    output,
    "wizer-initialize",
    &OptimizeOptions {
        hostcall_fuel: Some(512 * 1024 * 1024), // 512 MiB per hostcall
    },
).await?;
# Ok(())
# }

An explicit budget requires use-golem-wasmtime and Cargo patches selecting Golem's compatible Wasmtime 46.0.1 fork (see the commented patches in Cargo.toml); the feature alone does not select the fork. Stock Wasmtime does not expose this setting, and an explicit budget without the feature returns an error. optimize_component and OptimizeOptions::default() leave the engine default unchanged (128 MiB in Golem's fork). This limits bytes copied per hostcall, not Wasm instruction fuel or the total snapshot size. Raising it allows larger copies and increases potential host memory use; insufficient fuel can still trigger Wizer's existing snapshot-extraction panic.

Preview 3 is opt-in and evolving; Preview 2 (--target wasi-p2) remains the default and stable path.

Mappings

Exports

Top level exported functions

The following WIT code:

package demo:pkg;

world example {
  export hello: func() -> string;
}

must be implemented in JavaScript as:

export const hello = () => {
    return "Hello, world!";
};

The this is bound to the module object. The JS function name is always in camelCase.

Exported interfaces

Exported interfaces has to be exported from JavaScript as objects:

The following WIT example:

package demo:pkg;

interface sample-api {
  get-string-length: func(value: string) -> u64;
}

world example {
  export sample-api;
}

has to be implemented in JavaScript as:

export const sampleApi = {
    getStringLength: (value) => {
        return value.length;
    }
};

All names are converted to camelCase. The JavaScript this is bound to object representing the exporter interface, in the above example it is sampleApi.

If two exported interfaces in the same world map to the same JavaScript object name, the colliding interfaces are exported with a qualified name derived from their full WIT interface id. For example, test:a/guest@1.0.0 and test:b/guest@1.0.0 both have the short interface name guest, so they must be exported as:

export const testA100Guest = {
    invoke: (a, b, c) => `${a}:${b}:${c}`,
};

export const testB100Guest = {
    invoke: (a, b, c, d, e) => `${a}:${b}:${c}:${d}:${e}`,
};

Interfaces whose JavaScript object names do not collide keep the short camelCase export shape.

Exported resources

Exported resources are implemented as classes in JS:

The following WIT example:

package demo:pkg;

interface iface {
  resource example-resource {
    constructor(name: string);
    get-name: func() -> string;
    compare: static func(h1: borrow<example-resource>, h2: borrow<example-resource>) -> s32;
    merge: static func(h1: own<example-resource>, h2: own<example-resource>) -> hello;
  }
}

world example {
  export iface;
}

Must be exported from JavaScript in the following way:

class Hello {
    constructor(name) {
        this.name = name;
    }

    // async to demonstrate it is possible
    async getName() {
        return this.name;
    }

    static compare(h1, h2) {
        if (h1.name === h2.name) {
            return 0;
        } else if h1.name < h2.name) {
            return -1;
        } else {
            return 1;
        }
    }

    static merge(h1, h2) {
        return new Hello(`${h1.name} & ${h2.name}`);
    }
}

export const iface = {
    Hello: Hello,
};

The classes have a UpperCamelCase name and their methods are in camelCase. All methods and static methods can be either sync or async.

Types

Name	WIT	JS	Notes
Character	`char`	`string`	-
String	`string`	`string`	-
Signed 8-bit integer	`s8`	`number`	-
Unsigned 8-bit integer	`u8`	`number`	-
Signed 16-bit integer	`s16`	`number`	-
Unsigned 16-bit integer	`u16`	`number`	-
Signed 32-bit integer	`s32`	`number`	-
Unsigned 32-bit integer	`u32`	`number`	-
Signed 64-bit integer	`s64`	`bigint`	-
Unsigned 64-bit integer	`u64`	`bigint`	-
32-bit float	`f32`	`number`	-
64-bit float	`f64`	`number`	-
Optional type	`option<T>`	`T \| undefined`	Nested options are encoded differently
List	`list<T>`	`T[]`	-
Result	`result<T, E>`	`{ tag: "ok": val: T } \| { tag: "err", val: E }`	-
Tuple	`tuple<A, B, C>`	Array	-
Enum	`enum { a, b, c}`	`"a" \| "b" \| "c"`	The strings match the WIT enum cases
Flags	`flags { a, b, c }`	`{ a: boolean, b: boolean, c: boolean }`	The object keys are camelCase
Record	`record { .. }`	Object	Field names are camelCase
Variant	`variant { .. }`	`{ tag: "x", val: X }`	Tag names match the WIT variant case names; `val` is undefined for unit cases
Future	`future<T>`	`Promise<T>`	WASI Preview 3 (`--target wasi-p3`) only
Stream	`stream<T>`	`AsyncIterable<T>`	WASI Preview 3 (`--target wasi-p3`) only

Imported result errors

An imported function that returns result<T, E> returns T on success and throws E on failure. Async imports reject with the same error value.

Structured error values retain their WIT representation. String(error), template interpolation, and new Error(error).message render the payload as JSON instead of [object Object]. For example, a permission error renders as {"tag":"permission-denied"}, and a backend error renders as {"tag":"backend-error","val":"service unavailable"}. Bigint fields render as decimal strings without changing the original values.

The coercion methods are non-enumerable. The original fields, object identity, enumerable keys, and typed catch-and-rethrow behavior remain unchanged. Primitive errors and successful values are not decorated. This rendering applies to error string coercion; it does not replace the runtime's uncaught-exception formatter.

Limitations

Maximum number of function parameters is 26
Anonymous interface exports/imports are not supported
Imported individual functions into the world are not supported (only whole interfaces)
Preview 3 synchronous exports cannot return future<T> or stream<T>, directly or nested; use async func
Preview 3 exported top-level result<T, E> error arms cannot contain future<T> or stream<T>

Available JavaScript APIs

APIs

Web Platform APIs

Console

If the logging feature flag is enabled in the generated crate, it depends on wasi:logging, otherwise just on the core WASI interfaces.

assert, clear, count, countReset, debug, dir, dirXml, error, group, groupCollapsed, groupEnd, info, log, table, time, timeEnd, timeLog, trace, warn

HTTP (fetch)

Only if the http feature flag is enabled in the generated crate. It depends on wasi:http.

fetch, Headers, Request, Response, FormData, Blob, File

URL

URL (createObjectURL, revokeObjectURL)
URLSearchParams

Streams

Implemented by https://github.com/MattiasBuelens/web-streams-polyfill

ByteLengthQueuingStrategy, CountQueuingStrategy
ReadableStream, ReadableStreamDefaultReader, ReadableStreamBYOBReader, ReadableStreamDefaultController, ReadableByteStreamController, ReadableStreamBYOBRequest
WritableStream, WritableStreamDefaultController
TransformStream, TransformStreamDefaultController

Timers

setTimeout, clearTimeout, setInterval, clearInterval, setImmediate

Abort Controller

AbortController, AbortSignal, DOMException

Encoding

TextEncoder, TextDecoder, TextDecoderStream, TextEncoderStream

Messaging

MessageChannel, MessagePort

Events

Event, EventTarget, CustomEvent

Intl (Internationalization)

Minimal en-US implementation for library compatibility. All locale inputs are accepted but resolved to en-US.

Intl.DateTimeFormat — format(), formatToParts(), resolvedOptions(), supportedLocalesOf()
Intl.NumberFormat — format(), formatToParts(), resolvedOptions(), supportedLocalesOf()
Intl.Collator — compare(), resolvedOptions(), supportedLocalesOf()
Intl.PluralRules — select(), selectRange(), resolvedOptions(), supportedLocalesOf()
Intl.getCanonicalLocales(), Intl.supportedValuesOf()

When the timezone feature is enabled (default), DateTimeFormat supports all ~590 IANA timezones via chrono-tz.

Crypto (global)

crypto.randomUUID, crypto.getRandomValues

Performance (global)

performance.now() uses the WASI monotonic clock and is not affected by wall-clock adjustments.
performance.timeOrigin is the deployment wall-clock origin paired with that monotonic timeline.
The global object is shared with node:perf_hooks.

Structured Clone

structuredClone preserves object graphs, ArrayBuffer/view aliases and genuine in-memory Blob data. The runtime-owned process.env clones into an ordinary, independent environment snapshot; application-created proxies remain uncloneable. CryptoKey metadata participates in the same graph, including aliases and cycles. Transfer buffers detach only after the complete graph and host metadata validate; unlike Node.js, a rejected CryptoKey metadata graph leaves these buffers attached. ArrayBuffer transfer and runtime-local transferable AbortSignals are supported. Transferred signal reasons are copied before local abort listeners run; target abort delivery is queued. Clone/transfer markers are enforced by the same private policy used by MessageChannel; nonstandard json/lossy options cannot disable rejection. Blob clones own independent byte data. File-backed/foreign Blob backing, SharedArrayBuffer or immutable ArrayBuffer cloning, resizable-ArrayBuffer-backed views, and stream/MessagePort/FileHandle transfer are unsupported and rejected. FileHandle and web-stream payloads also reject without a transfer list; their ownership transfer is unavailable. Execution-job results reject Blob and other host values rather than transporting opaque resources. The serializer is adapted from https://github.com/ungap/structured-clone.

Node.js-Compatible Modules

node:assert

ok, equal, notEqual, strictEqual, notStrictEqual
deepEqual, notDeepEqual, deepStrictEqual, notDeepStrictEqual, partialDeepStrictEqual
throws, doesNotThrow, rejects, doesNotReject
ifError, match, doesNotMatch, fail
AssertionError, CallTracker
strict — strict mode variant (re-maps equal → strictEqual, deepEqual → deepStrictEqual, etc.)

node:async_hooks

AsyncLocalStorage — run, exit, getStore, enterWith, disable, snapshot, bind
AsyncResource — runInAsyncScope, asyncId, triggerAsyncId, bind
createHook — stub (returns enable/disable no-ops)
executionAsyncId, triggerAsyncId, executionAsyncResource — stubs

Context propagation works through Promise.prototype.then/catch/finally and setTimeout/setInterval. Limitation: QuickJS await uses internal C-level perform_promise_then which bypasses JS-visible Promise.prototype.then, so context is not propagated across await boundaries.

node:buffer

Buffer, Blob, File, SlowBuffer
resolveObjectURL, isAscii, isUtf8
INSPECT_MAX_BYTES, kMaxLength, kStringMaxLength, constants

node:child_process

WASI cannot create host processes. JavaScript commands targeting process.execPath and executable Node shebang files run in the component. On Preview 3, each local child has a fresh runtime, argv, environment, cwd and module cache. Synchronous calls pause parent JavaScript while the child drains its referenced work. Local spawn and execFile expose live output and let the parent run while the child waits for timers or I/O. JavaScript execution is cooperative on the shared WASM thread: a CPU-bound child needs its own timeout; parent timers cannot preempt it to call kill(). Nested children inherit the outer child's deadline. The constrained local exec and fork adapters still execute synchronously before delivering their events. Preview 2 retains inline execution and does not join asynchronous local-child work. The constrained compatibility adapter also recognizes npm's literal sh -c form for plain Node commands. Unsupported shells, shell syntax, external executables and unsupported shebangs fail explicitly with ENOSYS, unless an embedding handles them through a registered backend.

ChildProcess, exec, execFile, fork, spawn, execSync, execFileSync, spawnSync

An embedding may register command fallbacks through wasm-rquickjs:child-process (below). Without a backend, the unsupported-command behavior is unchanged. exec and execFile collect the asynchronous backend child's output, preserve its error or exit status, and enforce their output limits and timeout. They do not use the synchronous backend when an asynchronous command is accepted. Promisified exec and execFile return both output channels and expose their child through the promise's child property.

Preview 3 local children capture exit status and uncaught failures, preserve piped bytes, and support timeout, cancellation and bounded output. Fixed input is available through process.stdin, fs.readFile(0) / fs.readFileSync(0) and /dev/stdin. Live writes to child.stdin, interactive stdin, extra file descriptors and IPC are not provided; unsupported stdio requests fail with ENOSYS. Inherited output passes through the parent's stream adapter and has a 64 MiB per-channel transfer limit. Fresh children do not provide hard JavaScript termination after process.exit(). Native embedding modules must compose their child work explicitly rather than spawning unrelated wit-bindgen tasks across the synchronous child boundary. Runtime-init hooks must stay lazy.

node:cluster (stub)

Compatibility stubs — clustering is not supported in WASM.

isPrimary, isMaster, isWorker, fork, disconnect, setupPrimary

node:constants

Merged constants from os.constants, fs.constants, and crypto.constants (signal numbers, errno values, file flags, etc.)

node:crypto

Hashing: createHash, createHmac, hash, getHashes
Ciphers: createCipheriv, createDecipheriv, getCiphers
- Supported: aes-128/256-cbc, aes-128/256-ctr, aes-128/256-gcm, aes-128/192/256-wrap, id-aes128/192/256-wrap, id-aes128/192/256-wrap-pad, des-ede3-cbc, des3-wrap, chacha20-poly1305
Signing: createSign, createVerify (Ed25519, ECDSA with P-256, P-384, secp256k1)
Keys: createPublicKey, createPrivateKey, createSecretKey, KeyObject, generateKeyPairSync, generateKeyPair
ECDH: createECDH, ECDH, diffieHellman, getCurves
Certificate: Certificate (verifySpkac, exportPublicKey, exportChallenge)
Random: randomBytes, randomFillSync, randomFill, randomInt, randomUUID, pseudoRandomBytes, prng, rng
KDF: pbkdf2, pbkdf2Sync, scrypt, scryptSync, hkdf, hkdfSync
Primes: generatePrime, generatePrimeSync, checkPrime, checkPrimeSync
Other: timingSafeEqual, getFips, setFips, secureHeapUsed

node:dgram

UDP datagram sockets built on WASI sockets.

dgram.createSocket(type[, listener]) — create a UDP socket (udp4 or udp6)
socket.bind, socket.send, socket.sendto, socket.connect, socket.disconnect, socket.close
socket.address(), socket.remoteAddress()
socket.setTTL, socket.setRecvBufferSize / getRecvBufferSize, socket.setSendBufferSize / getSendBufferSize
socket.ref() / socket.unref() — no-op
Events: message, listening, close, error, connect

Not supported: multicast operations (setBroadcast, setMulticastTTL, addMembership, etc.) throw ENOSYS.

node:diagnostics_channel

Publish/subscribe diagnostic messaging and tracing.

Subscriber and store-transform errors are delivered through uncaughtException on the next tick, without interrupting other subscribers.

channel(name), subscribe(name, onMessage), unsubscribe(name, onMessage), hasSubscribers(name), tracingChannel(name)
Channel — subscribe, unsubscribe, publish, bindStore, unbindStore, runStores, hasSubscribers, name
TracingChannel — subscribe, unsubscribe, hasSubscribers, traceSync, tracePromise, traceCallback

Built-in HTTP diagnostics channels: http.client.request.created, http.client.request.start, http.client.request.error, http.client.response.finish.

node:dns

DNS resolution via WASI sockets.

lookup, lookupService, resolve, resolve4, resolve6
resolveAny, resolveCname, resolveCaa, resolveMx, resolveNaptr, resolveNs, resolvePtr, resolveSoa, resolveSrv, resolveTxt, resolveTlsa
reverse, setServers, getServers, setDefaultResultOrder, getDefaultResultOrder
Resolver class
promises — promise-based API
Error constants: NODATA, FORMERR, SERVFAIL, NOTFOUND, NOTIMP, REFUSED, BADQUERY, BADNAME, BADFAMILY, BADRESP, CONNREFUSED, TIMEOUT, EOF, FILE, NOMEM, DESTRUCTION, BADSTR, BADFLAGS, NONAME, BADHINTS, NOTINITIALIZED, LOADIPHLPAPI, ADDRGETNETWORKPARAMS, CANCELLED, ADDRCONFIG, V4MAPPED, ALL

node:domain

Deprecated error-handling domains (sync-only).

domain.create() / domain.createDomain(), domain.active, domain._stack
Domain class (extends EventEmitter): run, add, remove, bind, intercept, enter, exit, dispose, members, parent
process.domain — reflects active domain
Error decoration: error.domain, error.domainEmitter, error.domainBound, error.domainThrown
EventEmitter integration and async propagation via process.nextTick, setTimeout, setInterval

Limitation: No async context propagation via async_hooks — only synchronous errors and explicitly bound callbacks are captured.

node:events

EventEmitter — on, once, off, addListener, removeListener, removeAllListeners, emit, listenerCount, eventNames, listeners, rawListeners, prependListener, prependOnceListener, setMaxListeners, getMaxListeners
Static: once, on, getEventListeners, getMaxListeners, setMaxListeners, addAbortListener, errorMonitor, captureRejections
Event, EventTarget, CustomEvent

node:fs

Comprehensive filesystem API built on WASI filesystem.

Symbolic links are persistent WASI filesystem objects, so linked package trees remain visible to later fresh execution runtimes. Link targets must be relative: Rooted targets cannot be resolved within a WASI preopen, so symlink fails with EINVAL without creating an object when given one. Production Golem and macOS/Linux local development support these links. Windows local development currently requires Developer Mode or an equivalent symlink privilege; non-link filesystem and npm workflows are unaffected.

Sync: readFileSync, writeFileSync, appendFileSync, openSync, closeSync, readSync, writeSync, ftruncateSync, fsyncSync, fdatasyncSync, statSync, lstatSync, fstatSync, statfsSync, readdirSync, accessSync, existsSync, realpathSync, truncateSync, copyFileSync, linkSync, symlinkSync, readlinkSync, chmodSync, fchmodSync, lchmodSync, chownSync, fchownSync, lchownSync, utimesSync, futimesSync, lutimesSync, unlinkSync, renameSync, mkdirSync, rmdirSync, rmSync, mkdtempSync, opendirSync, readvSync, writevSync, cpSync
Async (callback): readFile, writeFile, appendFile, open, close, read, write, stat, lstat, fstat, statfs, ftruncate, fsync, fdatasync, readdir, access, exists, realpath, truncate, copyFile, link, symlink, readlink, chmod, fchmod, lchmod, chown, fchown, lchown, utimes, futimes, lutimes, unlink, rename, mkdir, rmdir, rm, mkdtemp, opendir, watch, watchFile, unwatchFile, readv, writev, cp, openAsBlob
Streams: createReadStream, createWriteStream
Classes: Stats, Dirent, Dir, FSWatcher, StatWatcher, ReadStream, WriteStream
Constants: F_OK, R_OK, W_OK, X_OK, O_RDONLY, O_WRONLY, O_RDWR, O_CREAT, O_EXCL, O_TRUNC, O_APPEND, etc.

node:fs/promises

Promise-based filesystem API.

FileHandle, open, readFile, writeFile, appendFile, unlink, rename, mkdir, rmdir, rm, stat, lstat, readdir, opendir, access, realpath, truncate, copyFile, link, symlink, readlink, chmod, lchmod, chown, lchown, utimes, lutimes, mkdtemp, cp, watch, statfs, constants

node:http / node:https

Requires the http feature flag. Client requests use wasi:http (TLS handled transparently). Server support uses wasi:sockets for TCP-level HTTP/1.1 serving.

http.request(url|options[, callback]), http.get(url|options[, callback])
http.METHODS, http.STATUS_CODES, http.maxHeaderSize
http.validateHeaderName, http.validateHeaderValue
http.Agent, http.globalAgent
http.OutgoingMessage — base class for writable HTTP message objects
http.ClientRequest — write, end, setHeader, getHeader, removeHeader, hasHeader, getHeaderNames, getHeaders, getRawHeaderNames, flushHeaders, setNoDelay, setSocketKeepAlive, abort, destroy, setTimeout
http.IncomingMessage — statusCode, statusMessage, headers, rawHeaders, httpVersion
https.request / https.get — delegates to http (WASI-HTTP handles TLS transparently)
http.createServer([options][, requestListener]) — create an HTTP/1.1 server (requires wasi:sockets)
http.Server (extends net.Server): listen, close, closeAllConnections, closeIdleConnections, setTimeout, maxRequestsPerSocket; emits dropRequest when the per-socket limit is exceeded
http.ServerResponse (extends EventEmitter): writeHead, setHeader, getHeader, removeHeader, hasHeader, getHeaders, getHeaderNames, getRawHeaderNames, write, end, flushHeaders, writeContinue, writeProcessing, writeEarlyHints, cork, uncork
Server-side IncomingMessage (extends stream.Readable): method, url, headers, headersDistinct, rawHeaders, httpVersion, socket, client, complete, aborted, trailers, trailersDistinct, rawTrailers
node:_http_common — _checkIsHttpToken, _checkInvalidHeaderChar
Supported features: keep-alive connections, chunked transfer encoding, content-length bodies, ordered pipelined responses, server-side 100/102/103 informational responses, per-socket request limits, idle connection cleanup

Not yet supported: HTTP Upgrade and CONNECT tunnels, client-side 1xx informational events through wasi:http, server-side timeout enforcement, https.createServer() / HTTPS server, client lookup / autoSelectFamily options, and custom per-request createConnection transports. Custom Agent createConnection hooks are ignored with a warning so Agent metadata and scheduling remain usable, but they cannot route or isolate traffic; every outbound request still uses wasi:http.

node:http2 (stub)

Compatibility stubs — HTTP/2 is not supported.

connect, createServer, createSecureServer, Http2ServerRequest, Http2ServerResponse

wasm-rquickjs:child-process

setProcessBackend({ spawn?, spawnSync? }) installs runtime-local command fallbacks; pass null or undefined to clear them. Methods receive (command, args, options) and return undefined when they do not handle a command. Local Node and executable Node-shebang targets retain priority. The optional-argv forms spawn(command, options) and spawnSync(command, options) are normalized before dispatch, so adapters always receive an argv array and a separate options object. spawn returns a ChildProcess-compatible object. spawnSync returns a synchronous Node-style result with byte stdout/stderr, or null for unpiped channels; the wrapper applies the requested output encoding. A Promise from spawnSync is rejected. execFileSync uses that fallback; execSync delegates with the shell option set. This hook does not itself execute host processes or implement a tool registry, permissions, or shell policy.

Embeddings can supply an additional JS module named wasm-rquickjs-runtime-init using --js-modules. It is imported after builtin wiring and before entry code in both the main runtime and every fresh execution job. Use it to register adapters independently in each runtime. It also runs during Wizer initialization: registration must not discover tools, capture invocation authority, perform host I/O, or start background work. Do that lazily in backend methods instead. This configuration hook is not a security boundary; host capability checks remain authoritative.

wasm-rquickjs:execution

Runs JavaScript asynchronously in a fresh QuickJS runtime. startJavaScript(options) returns live stdout/stderr readable streams, a result promise resolving to { value, overflowed }, and cancel(). Jobs are runtime-only; importing this module during pre-initialization is safe. runJavaScript(options) collects the streams and resolves to { value, overflowed, stdout, stderr }. value crosses the runtime boundary through structured clone.

Options accept exactly one of entry: string or inline source: string, plus cwd, argv, env, timeoutMs, maxBytes (1 MiB per stream by default, 64 MiB maximum), and overflow (terminate by default or truncate). language: "javascript" | "typescript" applies only to inline source and defaults to JavaScript. With the generated crate's typescript-runtime feature enabled, TypeScript entry files are selected by their .ts, .mts, or .cts extension, and inline jobs can select language: "typescript". Output and completion wake the parent without periodic polling. Timeout budgets start after child-runtime initialization. An async wait observes deadlines while jobs yield; for non-yielding JavaScript, the QuickJS interrupt handler samples the clock at an adaptive stride targeting one check per 10% of timeoutMs during steady CPU work. This is a best-effort budget, not an exact cutoff or a maximum-overrun guarantee. A job that finishes between checks can succeed after its literal deadline; no extra clock check occurs at completion. Entry modules run for their side effects; an exported default function (or run function when there is no default function) is invoked and awaited. Relative entry paths and imports resolve from cwd. Inline source is an async function body: top-level await and return are supported, while static import/export declarations are not. env is an explicit allowlist and defaults to an empty environment; jobs never merge or inherit the enclosing component's environment variables. When argv is omitted, entry jobs receive ["wasm-rquickjs-execution", resolvedEntryPath] and inline jobs receive ["wasm-rquickjs-execution"]. With overflow: "terminate", exceeding either stream's bound rejects the job. With overflow: "truncate", execution continues, captured output is bounded, and overflowed is true when either stream exceeded the bound. Cancellation is cooperative for queued or yielding code and cannot preempt a tight loop already running on the same thread; a positive timeoutMs is the best-effort escape mechanism for such a loop. Cancellation remains a guest-local flag check on every QuickJS interrupt. A job that never settles must be cancelled or given a timeout before the enclosing component invocation can finish. A runtime accepts at most eight active jobs, and child executions cannot recursively create more execution jobs. Fresh-runtime execution means fresh JavaScript globals, process state, timers, module caches, and other mutable QuickJS runtime state. Results cross the runtime boundary through structured clone. It is not a security sandbox: execution code inherits the component's filesystem, network, clocks, randomness, and other available host capabilities, and cwd is only a resolution base—not a filesystem boundary. Failed jobs are currently returned as parent-realm Error messages rather than structured-cloned thrown values.

This API is distinct from node:vm. The node:vm module provides synchronous Node-compatible contexts within one QuickJS runtime, including live-object behavior required by its API. wasm-rquickjs:execution provides asynchronous jobs in fresh runtimes with structured-clone results. Neither API is a security sandbox, and both share the enclosing component's capabilities and filesystem access.

node:inspector (stub)

Compatibility stubs — no V8 inspector in WASM.

Session, open, close, url, waitForDebugger, console, Network

node:module

Builtin ESM export names are fixed by the runtime, including aliases. Changing builtin properties before the first ESM import does not add or remove named exports; syncBuiltinESMExports() updates their values.

require, require.resolve, createRequire, builtinModules, isBuiltin, runMain, _nodeModulePaths
stripTypeScriptTypes(code[, options]) with Node-compatible strip and transform modes when the generated crate enables typescript-runtime
Package resolution supports package.json main, exports root/subpath maps, wildcard exports patterns, imports maps, and wildcard imports patterns. CJS resolution recognizes golem, node, require, module-sync, and default conditions; ESM resolution recognizes golem, node, import, module-sync, and default. Package imports can target relative files, external packages, and node: builtins.
With typescript-runtime, .mts is always ESM, .cts is always CommonJS, and .ts follows the nearest package type and Node-style syntax classification. ESM imports require explicit file extensions. Type stripping inside node_modules is rejected, matching Node's built-in support. The runtime does not type-check, read tsconfig.json, or support .tsx; enable typescript-transform-runtime instead of typescript-runtime for enums, runtime namespaces, and other transform-required syntax in module files or inline language: "typescript" execution source.

node:net

TCP sockets and servers built on WASI sockets.

net.createServer([options][, connectionListener]), net.createConnection(options[, connectListener]), net.connect(...)
net.isIP(input) / net.isIPv4(input) / net.isIPv6(input)
net.getDefaultAutoSelectFamily() / net.setDefaultAutoSelectFamily(value) — stubs
net.Socket (extends stream.Duplex): connect, write, end, destroy, resetAndDestroy, setTimeout, setNoDelay, setKeepAlive, address, ref, unref
- Properties: remoteAddress, remotePort, remoteFamily, localAddress, localPort, localFamily, bytesRead, bytesWritten, connecting, pending, readyState
- Events: connect, ready, data, end, close, error, timeout, drain, lookup
net.Server (extends EventEmitter): listen, close, address, getConnections, ref, unref
- Properties: listening, maxConnections
- Events: listening, connection, close, error, drop
net.BlockList, net.SocketAddress, net.Stream

Not supported: IPC/Unix domain sockets, Happy Eyeballs/autoSelectFamily (stubbed), cluster integration.

node:os

arch, platform, type, release, version, machine, hostname, homedir, tmpdir, endianness
cpus, loadavg, freemem, totalmem, uptime, availableParallelism
networkInterfaces, userInfo, getPriority, setPriority
EOL, devNull, constants (signals, errno, priority)

node:path

sep, delimiter, basename, dirname, extname, isAbsolute, join, normalize, relative, resolve, parse, format, matchesGlob, toNamespacedPath, posix

node:perf_hooks

performance — monotonic now(), deployment timeOrigin, mark(), measure(), getEntries(), getEntriesByName(), getEntriesByType(), clearMarks(), clearMeasures(), toJSON()
PerformanceEntry, PerformanceObserver
monitorEventLoopDelay, createHistogram, constants

node:process

Properties: argv, argv0, env, pid, ppid, platform ('wasi'), arch ('wasm32'), version, versions, config, features, execArgv, execPath, exitCode, stdout, stderr
Methods: exit(code), cwd(), nextTick(callback, ...args), getBuiltinModule(id), hrtime(), hrtime.bigint(), uptime(), cpuUsage(), memoryUsage(), kill(pid, signal), abort(), emitWarning()
getBuiltinModule(id) returns the existing object for builtins registered by this runtime, and undefined for unavailable IDs. The supported set is smaller than Node.js: node:sea, node:test/reporters, node:inspector/promises, node:wasi, _stream_wrap, and unimplemented _http_*/_tls_* wrappers are unavailable.
User/Group: getuid, getgid, geteuid, getegid, getgroups, setuid, setgid
Inherits from EventEmitter — supports on('uncaughtException'), on('unhandledRejection'), etc.

node:punycode

decode, encode, toASCII, toUnicode, ucs2, version

node:querystring

stringify / encode, parse / decode, escape, unescape, unescapeBuffer

node:readline

createInterface, Interface, clearLine, clearScreenDown, cursorTo, moveCursor, emitKeypressEvents
readline/promises — promise-based API

node:repl (stub)

start, REPLServer, Recoverable, builtinModules

node:sqlite

Requires the sqlite feature flag. Provides a synchronous SQLite database API with an embedded SQLite engine.

DatabaseSync — prepare, exec, close, open, isOpen, isTransaction, createSession, applyChangeset, enableLoadExtension, function, aggregate, backup
StatementSync — run, get, all, iterate, columns, setReadBigInts, setAllowBareNamedParameters, sourceSQL, expandedSQL
Session — changeset, patchset, close
Constants: SQLITE_CHANGESET_OMIT, SQLITE_CHANGESET_REPLACE, SQLITE_CHANGESET_ABORT

Not supported: loadExtension() (throws — native extensions cannot be loaded in WASM).

node:stream

Legacy _stream_readable, _stream_writable, _stream_duplex, _stream_transform and _stream_passthrough aliases support CommonJS and ESM, with the same constructor defaults.
Readable (with from, fromWeb, toWeb, wrap, and functional methods: map, filter, flatMap, take, drop, toArray, forEach, reduce, some, every, find)
Writable, Duplex, Transform, PassThrough, Stream
pipeline, finished, compose, duplexPair, addAbortSignal
getDefaultHighWaterMark, setDefaultHighWaterMark, isDisturbed, destroy
stream/consumers (arrayBuffer, blob, buffer, json, text)
stream/promises — promise-based pipeline and finished

node:string_decoder

StringDecoder

node:test

Built-in test runner.

test, describe / suite, it, before, after, beforeEach, afterEach
mock — function mocking utilities
run — programmatic test execution

node:timers

setTimeout, setInterval, setImmediate, clearTimeout, clearInterval
timers/promises — promise-based setTimeout, setInterval, setImmediate

node:tls (stub)

Compatibility stubs — TLS is handled transparently by the WASI-HTTP layer.

SecureContext, TLSSocket, Server, connect, createServer, createSecureContext, checkServerIdentity, getCiphers, rootCertificates
DEFAULT_MIN_VERSION, DEFAULT_MAX_VERSION, DEFAULT_ECDH_CURVE

node:trace_events

Partial compatibility API to unblock modules that inspect tracing state.

createTracing({ categories: string[] }) — creates a Tracing handle
Tracing#enable() / Tracing#disable() — toggles local tracing state
Tracing#enabled / Tracing#categories — read tracing configuration
getEnabledCategories() — returns currently enabled categories as a comma-separated string

Limitation: No native trace sink; API-surface compatibility only.

node:tty

isatty, ReadStream, WriteStream

node:url

URL, URLSearchParams
parse, resolve, format (legacy API)
domainToASCII, domainToUnicode
fileURLToPath, pathToFileURL, urlToHttpOptions

node:util

sys / node:sys aliases share the util object and support CommonJS and ESM.
format, inspect, deprecate, debugLog, log
Type checks: isArray, isBoolean, isNull, isNullOrUndefined, isNumber, isString, isSymbol, isUndefined, isRegExp, isObject, isDate, isError, isFunction, isPrimitive, isBuffer
promisify, callbackify
parseEnv, styleText, getCallSite, getCallSites, toUSVString, _extend
TextEncoder, TextDecoder

node:v8

getHeapStatistics, getHeapSpaceStatistics, getHeapSnapshot, getHeapCodeStatistics
setFlagsFromString, writeHeapSnapshot, takeCoverage, stopCoverage
serialize, deserialize, Serializer, Deserializer, DefaultSerializer, DefaultDeserializer

node:vm

runInNewContext, runInContext, runInThisContext, createContext, isContext, compileFunction
Script, createScript
SourceTextModule (experimental, limited export const/export let/export var support)

These contexts are synchronous compatibility contexts within one QuickJS runtime. For asynchronous jobs in fresh runtimes with structured-clone results, use wasm-rquickjs:execution. Neither API is a security sandbox; both share the enclosing component's capabilities and filesystem access.

node:worker_threads (runtime-local messaging)

MessageChannel and MessagePort work within one runtime. Worker and BroadcastChannel construction throws immediately. Environment-data APIs are unavailable.

isMainThread, parentPort, workerData, threadId, resourceLimits
MessagePort, MessageChannel, receiveMessageOnPort
markAsUncloneable, markAsUntransferable, isMarkedAsUntransferable
moveMessagePortToContext (limited compatibility API; no external execution context)
Unsupported compatibility exports: Worker, BroadcastChannel, getEnvironmentData, setEnvironmentData

node:zlib

Classes: Deflate, Inflate, Gzip, Gunzip, DeflateRaw, InflateRaw, Unzip, BrotliCompress, BrotliDecompress
Factory: createGzip, createGunzip, createDeflate, createInflate, createDeflateRaw, createInflateRaw, createUnzip, createBrotliCompress, createBrotliDecompress
Async: gzip, gunzip, deflate, inflate, deflateRaw, inflateRaw, unzip, brotliCompress, brotliDecompress
Sync: gzipSync, gunzipSync, deflateSync, inflateSync, deflateRawSync, inflateRawSync, unzipSync, brotliCompressSync, brotliDecompressSync
crc32, constants, codes

Internal / Compatibility Modules

Additional internal modules

internal/url — isURL
internal/http — kOutHeaders symbol
base64-js — byteLength, toByteArray, fromByteArray
ieee754 — read, write

Compatibility Reports

NPM Library Compatibility Tracker — test results for popular npm packages
Node.js v22 Compatibility Report — per-test results for vendored Node.js test suite

Coming from QuickJS

Global:
- parseInt
- parseFloat
- isNaN
- isFinite
- quickMicrotask
- decodeURI
- decodeURIComponent
- encodeURI
- encodeURIComponent
- escape
- unescape
- Infinity
- NaN
- undefined
- [Symbol.toStringTag]
Object
- static methods and properties:
  - create
  - getPrototypeOf
  - setPrototypeOf
  - defineProperty
  - defineProperties
  - getOwnPropertyNames
  - getOwnPropertySymbols
  - groupBy
  - keys
  - values
  - entries
  - isExtensible
  - preventExtensions
  - getOwnPropertyDescriptor
  - getOwnPropertyDescriptors
  - is
  - assign
  - seal
  - freeze
  - isSealed
  - isFrozen
  - fromEntries
  - hasOwn
- methods and properties:
  - toString
  - toLocaleString
  - valueOf
  - hasOwnProperty
  - isPrototypeOf
  - propertyIsEnumerable
  - __proto__
  - __defineGetter__
  - __defineSetter__
  - __lookupGetter__
  - __lookupSetter__
Function
- methods and properties:
  - call
  - apply
  - bind
  - toString
  - [Symbol.hasInstance]
  - fileName
  - lineNumber
  - columnNumber
Error
- methods and properties:
  - name
  - message
  - toString
- static methods and properties:
  - isError
  - captureStackTrace
  - stackTraceLimit
  - prepareStackTrace
Generator
- methods and properties:
  - next
  - return
  - throw
  - [Symbol.toStringTag]
- static methods and properties:
  - from
Iterator
- static methods and properties:
  - from
- methods and properties:
  - drop filter flatMap map take every find forEach some reduce toArray [Symbol.iterator] [Symbol.toStringTag]
Array
- static methods and properties:
  - isArray
  - from
  - of
  - [Symbol.species]
- methods and properties:
  - at
  - with
  - concat
  - every
  - some
  - forEach
  - map
  - filter
  - reduce
  - reduceRight
  - fill
  - find
  - findIndex
  - findLast
  - findLastIndex
  - indexOf
  - lastIndexOf
  - includes
  - join
  - toString
  - toLocaleString
  - pop
  - push
  - shift
  - unshift
  - reverse
  - toReversed
  - sort
  - toSorted
  - slice
  - splice
  - toSpliced
  - copyWithin
  - flatMap
  - flat
  - values
  - [Symbol.iterator]
  - keys
  - entries
Number
- static methods and properties:
  - parseInt
  - parseFloat
  - isNaN
  - isFinite
  - isInteger
  - isSafeInteger
  - MAX_VALUE
  - MIN_VALUE
  - NaN
  - NEGATIVE_INFINITY
  - POSITIVE_INFINITY
  - EPSILON
  - MAX_SAFE_INTEGER
  - MIN_SAFE_INTEGER
- methods and properties:
  - toExponential
  - toFixed
  - toPrecision
  - toString
  - toLocaleString
  - valueOf
Boolean
- methods and properties:
  - toString
  - valueOf
String
- static methods and properties:
  - fromCharCode
  - fromCodePoint
  - raw
- methods and properties:
  - length
  - at
  - charCodeAt
  - charAt
  - concat
  - codePointAt
  - isWellFormed
  - toWellFormed
  - indexOf
  - lastIndexOf
  - includes
  - endsWith
  - startsWith
  - match
  - matchAll
  - search
  - split
  - substring
  - substr
  - slice
  - repeat
  - replace
  - replaceAll
  - padEnd
  - padStart
  - trim
  - trimEnd
  - trimRight
  - trimStart
  - trimLeft
  - toString
  - valueOf
  - localeCompare
  - normalize
  - toLowerCase
  - toUpperCase
  - toLocaleLowerCase
  - toLocaleUpperCase
  - [Symbol.iterator]
  - anchor
  - big
  - blink
  - bold
  - fixed
  - fontcolor
  - fontsize
  - italics
  - link
  - small
  - strike
  - sub
  - sup
Symbol
- static methods and properties:
  - for
  - keyFor
- methods and properties:
  - toString
  - valueOf
  - description
  - [Symbol.toPrimitive]
  - [Symbol.toStringTag]
Map
- static methods and properties:
  - groupBy
  - [Symbol.species]
- methods and properties:
  - set
  - get
  - has
  - delete
  - clear
  - size
  - forEach
  - values
  - keys
  - entries
  - [Symbol.iterator]
  - [Symbol.toStringTag]
Set
- static methods and properties:
  - [Symbol.species]
- methods and properties:
  - add
  - has
  - delete
  - clear
  - size
  - forEach
  - isDisjointFrom
  - isSubsetOf
  - isSupersetOf
  - intersection
  - difference
  - symmetricDifference
  - union
  - values
  - keys
  - [Symbol.iterator]
  - entries
  - [Symbol.toStringTag]
WeakMap
- methods and properties:
  - set
  - get
  - has
  - delete
  - [Symbol.toStringTag]
WeakSet
- methods and properties:
  - add
  - has
  - delete
  - [Symbol.toStringTag]
GeneratorFunction
- methods and properties:
  - [Symbol.toStringTag]
Math
- static methods and properties:
  - min
  - max
  - abs
  - floor
  - ceil
  - round
  - sqrt
  - acos
  - asin
  - atan
  - atan2
  - cos
  - exp
  - log
  - pow
  - sin
  - tan
  - trunc
  - sign
  - cosh
  - sinh
  - tanh
  - acosh
  - asinh
  - atanh
  - expm1
  - log1p
  - log2
  - log10
  - cbrt
  - hypot
  - random
  - f16round
  - fround
  - imul
  - clz32
  - sumPrecise
  - [Symbol.toStringTag]
  - E
  - LN10
  - LN2
  - LOG2E
  - LOG10E
  - PI
  - SQRT1_2
  - SQRT2
Reflect
- static methods and properties:
  - apply
  - construct
  - defineProperty
  - deleteProperty
  - get
  - getOwnPropertyDescriptor
  - getPrototypeOf
  - has
  - isExtensible
  - ownKeys
  - preventExtensions
  - set
  - setPrototypeOf
  - [Symbol.toStringTag]
RegExp
- static methods and properties:
  - escape
  - [Symbol.species]
- methods and properties:
  - flags
  - source
  - global
  - ignoreCase
  - multiline
  - dotAll
  - unicode
  - unicodeSets
  - sticky
  - hasIndices
  - exec
  - compile
  - test
  - toString
  - [Symbol.replace]
  - [Symbol.match]
  - [Symbol.matchAll]
  - [Symbol.search]
  - [Symbol.split]
JSON
- static methods and properties:
  - parse
  - stringify
  - [Symbol.toStringTag]
Promise
- static methods and properties:
  - resolve
  - reject
  - all
  - allSettled
  - any
  - try
  - race
  - withResolvers
  - [Symbol.species]
- methods and properties:
  - then
  - catch
  - finally
  - [Symbol.toStringTag]
AsyncFunction
- methods and properties:
  - [Symbol.toStringTag]
AsyncIterator
- methods and properties:
  - next
  - return
  - throw
AsyncGeneratorFunction
- methods and properties:
  - [Symbol.toStringTag]
AsyncGenerator
- methods and properties:
  - next
  - return
  - throw
  - [Symbol.toStringTag]
Date
- static methods and properties:
  - now
  - parse
  - UTC
- methods and properties:
  - valueOf
  - toString
  - [Symbol.toPrimitive]
  - toUTCString
  - toGMTString
  - toISOString
  - toDateString
  - toTimeString
  - toLocaleString
  - toLocaleDateString
  - toLocaleTimeString
  - getTimezoneOffset
  - getTime
  - getYear
  - getFullYear
  - getUTCFullYear
  - getMonth
  - getUTCMonth
  - getDate
  - getUTCDate
  - getHours
  - getUTCHours
  - getMinutes
  - getUTCMinutes
  - getSeconds
  - getUTCSeconds
  - getMilliseconds
  - getUTCMilliseconds
  - getDay
  - getUTCDay
  - setTime
  - setMilliseconds
  - setUTCMilliseconds
  - setSeconds
  - setUTCSeconds
  - setMinutes
  - setUTCMinutes
  - setHours
  - setUTCHours
  - setDate
  - setUTCDate
  - setMonth
  - setUTCMonth
  - setYear
  - setFullYear
  - setUTCFullYear
  - toJSON
BigInt
- static methods and properties:
  - asIntN
  - asUintN
- methods and properties:
  - toString
  - valueOf
  - [Symbol.toStringTag]
ArrayBuffer
- static methods and properties:
  - isView
  - [Symbol.species
- methods and properties:
  - byteLength
  - maxByteLength
  - resizeable
  - detached
  - resize
  - slice
  - transfer
  - transferToFixedLength
  - [Symbol.toStringTag]
SharedArrayBuffer
- static methods and properties:
  - [Symbol.species]
- methods and properties:
  - byteLength
  - maxByteLength
  - growable
  - grow
  - slice
  - [Symbol.toStringTag]
Typed arrays (Int8Array, Uint8Array, Int16Array, Uint16Array, Int32Array, Uint32Array, BigInt64Array, BigUint64Array, Float32Array, Float64Array, Float16Array)
- static methods and properties:
  - from
  - of
  - [Symbol.species]
- methods and properties:
  - length
  - at
  - with
  - buffer
  - byteLength
  - set
  - byteOffset
  - values
  - [Symbol.iterator]
  - keys
  - entries
  - [Symbol.toStringTag]
  - copyWithin
  - every
  - some
  - forEach
  - map
  - filter
  - reduce
  - reduceRight
  - fill
  - find
  - findIndex
  - findLast
  - findLastIndex
  - reverse
  - toReversed
  - slice
  - subarray
  - sort
  - toSorted
  - join
  - toLocaleString
  - indexOf
  - lastIndexOf
  - includes
DataView
- methods and properties:
  - buffer
  - byteLength
  - byteOffset
  - getInt8
  - getUint8
  - getInt16
  - getUint16
  - getInt32
  - getUint32
  - getBigInt64
  - getBigUint64
  - getFloat16
  - getFloat32
  - getFloat64
  - setInt8
  - setUint8
  - setInt16
  - setUint16
  - setInt32
  - setUint32
  - setBigInt64
  - setBigUint64
  - setFloat16
  - setFloat32
  - setFloat64
  - [Symbol.toStringTag]
Atomics
- static methods and properties:
  - add
  - and
  - or
  - sub
  - xor
  - exchange
  - compareExchange
  - load
  - store
  - isLockFree
  - pause
  - wait
  - notify
  - [Symbol.toStringTag]
Performance
- methods and properties:
  - now
WeakRef
- methods and properties:
  - deref
  - [Symbol.toStringTag]
FinalizationRegistry
- methods and properties:
  - register
  - unregister
  - [Symbol.toStringTag]
Callsite
- methods and properties: -isNative
  - getFileName
  - getFunction
  - getFunctionName
  - getColumnNumber
  - getLineNumber
  - [Symbol.toStringTag]
Proxy

Developing

There are a few important things to keep in mind when working on the project:

The skeleton crate can be opened and compiled separately when working on the APIs provided for JavaScript. Unfortunately we cannot use the Cargo.toml file name in it because that breaks Rust packaging - so before working on it, it has to be renamed to Cargo.toml and before committing back it has to be renamed back to Cargo.toml_.
If the skeleton crate was compiled for testing, and then wasm-rquickjs is compiled, the include_dir! macro is embedding everything from the skeleton directory including the target directory, resulting in slow compilation times and huge resulting binaries. Use the cleanup-skeleton.sh script to quickly remove the target directory from the skeleton crate.
Run tools/check-skeleton-clippy.sh to lint the supported Preview 2 and Preview 3 skeleton feature matrix. The helper temporarily symlinks Cargo.toml to the checked-in Cargo.toml_, directs output to the workspace-root target/ cache, preserves that cache, and removes the symlink on exit. If a skeleton-local target/ already exists, continue to use cleanup-skeleton.sh before embedding the skeleton.
Runtime and node compatibility tests support opt-in caches for faster local iteration. Select Node with nvm use 22.14.0, then use the artifact and Wasmtime caches explicitly:
```
WASM_RQUICKJS_TEST_ARTIFACT_CACHE=1 \
WASM_RQUICKJS_TEST_WASMTIME_CACHE=1 \
cargo test --test runtime --features use-golem-wasmtime -- module_resolution --report-time
```
These caches may reuse generated wrapper, optimized component, and compiled Wasmtime artifacts. Every test still creates fresh wasm memory, a fresh Wasmtime Store and component instance, a fresh WASI context and temporary directory, and fresh QuickJS runtime state. Do not group compatibility cases into one wasm instance.

WASM_RQUICKJS_TEST_DROP_CACHE=1 forces generated artifacts to be rebuilt and bypasses Wasmtime's filesystem cache. WASM_RQUICKJS_TEST_UNOPTIMIZED=1 skips Wizer pre-initialization for a shorter compile/test loop. WASM_RQUICKJS_TEST_PREPARED_COMPONENT_CACHE=1 reuses immutable prepared Engine/Linker/Component state on the normal TestInstance::new path.

For skeleton development, select a local performance profile:
```
tools/dev-test.sh p2 fast-start runtime <exact_test_filter>
tools/dev-test.sh p2 fast-run node_compat <test_filter>
tools/dev-test.sh p2 fast-run node_compat <test_filter> --test-threads 4
tools/dev-test.sh p3 standard runtime ':tag:group3'
```
fast-start skips Wizer and uses one worker to minimize latency to the first result. fast-run runs Wizer, precompiles a changed component once before parallel workers start, reuses prepared components, and uses eight workers. Both accelerated profiles read the skeleton externally, reuse generated artifacts and Wasmtime's filesystem cache, and use locked Cargo builds. standard uses the embedded skeleton with optional caches and parent precompilation disabled, normal Wizer optimization, and default test-runner behavior.

fast-run defaults to eight workers and fast-start to one; pass test-r's --test-threads N after the filter to override either default. The eight-worker default was measured on a 14-core Apple M3 Max MacBook Pro (10 performance cores, 4 efficiency cores, 36 GB RAM, macOS 26.5.1). Performance comparisons must report preparation time, test execution time, and total wall time separately: precompilation makes the execution phase much faster but adds preparation that is only recovered by a sufficiently large or repeated filter.

Acknowledgements

The builtin JS modules are based on the work of several other projects:

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Name		Name	Last commit message	Last commit date
.agents		.agents
.github		.github
crates		crates
examples		examples
src		src
tests		tests
tools		tools
vendor		vendor
.gitignore		.gitignore
.gitmodules		.gitmodules
.nvmrc		.nvmrc
AGENTS.md		AGENTS.md
Cargo.lock		Cargo.lock
Cargo.toml		Cargo.toml
LICENSE		LICENSE
README.md		README.md
cleanup-skeleton.sh		cleanup-skeleton.sh

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wasm-rquickjs

Introduction

Comparison with ComponentizeJS

Comparison with wasmedge-quickjs

Usage

Generating the wrapper crate

Choosing the WASI target

Native modules and dependencies

Generating TypeScript module definitions

Using with Golem

WASI Preview 3 target

Mappings

Exports

Top level exported functions

Exported interfaces

Exported resources

Types

Imported result errors

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Available JavaScript APIs

APIs

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