API documentation

These APIs uses native streams that is not 100% compatible with the Node.js Streams API. Server APIs like createSever provides limited functionality useful for testing purposes. Serverless applications typically don't expose servers. Some server options are not supported: highWaterMark, pauseOnConnect, keepAlive, noDelay, keepAliveInitialDelay

connect

createConnection

createServer

os

path

perf_hooks

performance is available globally

performance.now

process

process is available globally

stream

stream/promises

finished

pipeline

string_decoder

StringDecoder

timers

Also available globally

tty

isatty

url

Class

URL

URLSearchParams

Prototype methods

util

Important

Supported encodings: hex, base64, utf-8, utf-16le, windows-1252 and their aliases.

zlib

Convenience methods

LLRT API

llrt:hex

export function encode(
  value: string | Array | ArrayBuffer | Uint8Array
): string;
export function decode(value: string): Uint8Array;

llrt:timezone

Lightweight timezone support for LLRT. Provides timezone offset calculations and a minimal Intl.DateTimeFormat implementation for dayjs and similar library compatibility.

interface Timezone {
  /**
   * Get the UTC offset in minutes for a timezone at a given time.
   * Returns a positive value for timezones ahead of UTC (e.g., 540 for Asia/Tokyo)
   * and a negative value for timezones behind UTC (e.g., -420 for America/Denver).
   * Automatically handles DST transitions.
   */
  getOffset(timezone: string, epochMs: number): number;

  /**
   * List all available IANA timezone names.
   */
  list(): string[];
}

declare var Timezone: Timezone;

export { Timezone };

Example

import { Timezone } from "llrt:timezone";

// Get current offset for Denver (handles DST automatically)
const offset = Timezone.getOffset("America/Denver", Date.now());
// Returns -420 (UTC-7) in winter, -360 (UTC-6) in summer

// Check DST transition
const beforeDst = new Date("2024-03-09T12:00:00Z").getTime();
const afterDst = new Date("2024-03-11T12:00:00Z").getTime();
console.log(Timezone.getOffset("America/Denver", beforeDst)); // -420
console.log(Timezone.getOffset("America/Denver", afterDst)); // -360

// List all available timezones
const zones = Timezone.list();

Intl.DateTimeFormat

LLRT provides a minimal Intl.DateTimeFormat implementation focused on timezone support. This enables libraries like dayjs to work with timezone conversions transparently.

// Create a formatter for a specific timezone
const formatter = new Intl.DateTimeFormat("en-US", {
  timeZone: "America/Denver",
  hour12: false,
  year: "numeric",
  month: "2-digit",
  day: "2-digit",
  hour: "2-digit",
  minute: "2-digit",
  second: "2-digit",
});

// Format a date
const date = new Date("2022-03-02T15:45:34Z");
console.log(formatter.format(date)); // "03/02/2022, 08:45:34"

// Get formatted parts
const parts = formatter.formatToParts(date);
// [{ type: "month", value: "03" }, { type: "literal", value: "/" }, ...]

// Get resolved options
const options = formatter.resolvedOptions();
console.log(options.timeZone); // "America/Denver"

Date.prototype.toLocaleString with timezone

Date.prototype.toLocaleString is enhanced to support the timeZone option:

const date = new Date("2022-03-02T15:45:34Z");

// Convert to Denver time
console.log(date.toLocaleString("en-US", { timeZone: "America/Denver" }));
// "03/02/2022, 8:45:34 AM"

// Convert to Tokyo time
console.log(date.toLocaleString("en-US", { timeZone: "Asia/Tokyo" }));
// "03/03/2022, 12:45:34 AM"

Using with dayjs

The timezone module enables dayjs timezone support without polyfills:

const dayjs = require("dayjs");
const utc = require("dayjs/plugin/utc");
const timezone = require("dayjs/plugin/timezone");

dayjs.extend(utc);
dayjs.extend(timezone);

// Convert between timezones
const date = dayjs("2022-03-02T15:45:34Z");
console.log(date.tz("America/Denver").format()); // "2022-03-02T08:45:34-07:00"
console.log(date.tz("Asia/Tokyo").format()); // "2022-03-03T00:45:34+09:00"

// Get start of day in a specific timezone
const denver = date.tz("America/Denver");
console.log(denver.startOf("day").format()); // "2022-03-02T00:00:00-07:00"

llrt:qjs

interface MemoryInfo {
  malloc_size: number;
  malloc_limit: number;
  memory_used_size: number;
  malloc_count: number;
  memory_used_count: number;
  atom_count: number;
  atom_size: number;
  str_count: number;
  str_size: number;
  obj_count: number;
  obj_size: number;
  prop_count: number;
  prop_size: number;
  shape_count: number;
  shape_size: number;
  js_func_count: number;
  js_func_size: number;
  js_func_code_size: number;
  js_func_pc2line_count: number;
  js_func_pc2line_size: number;
  c_func_count: number;
  array_count: number;
  fast_array_count: number;
  fast_array_elements: number;
  binary_object_count: number;
  binary_object_size: number;
}
export function ComputeMemoryUsage(): MemoryInfo;

llrt:xml

A lightweight and fast XML parser and builder

export class XmlText {
  constructor(text: string);
  toString(): string;
}

export class XmlNode {
  constructor(name: string);
  withName(name: string): this;
  addAttribute(name: string, value: string): this;
  addChildNode(node: XmlNode | XmlText): this;
  removeAttribute(name: string): this;
  toString(): string;
}

type XmlParserOptions = {
    ignoreAttributes?: boolean;
    attributeNamePrefix?: string;
    textNodeName?: string;
    attributeValueProcessor?: (attrName: string, attrValue: string, jpath: string) => unknown;
    tagValueProcessor?: (attrName: string, attrValue: string, jpath: string, hasAttributes: boolean) => unknown;
}
export class XMLParser(options?: XmlParserOptions){
    parse(xml:string):object
}

llrt:util

export function dimensions(): [number, number];
export function load(path: string): any;
export function print(value: any): void;

Web Platform API

CONSOLE

Console

DOM

Important

There are some differences with the WHATWG standard. Mainly browser specific behavior is removed:

keepalive is always true
request.body can only be string, Array, ArrayBuffer or Uint8Array
response.body returns null. Use response.text(), response.json() etc
mode, credentials, referrerPolicy, priority, cache is not available/applicable