disposable-lock

🔒 A tiny, modern wrapper around the Web Locks API
Provides a clean Promise-based and async dispose-friendly interface for lock management.

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Features

• 🧩 Minimal and dependency-free — pure TypeScript
• 🔁 Promise-based lifecycle with release()
• 🪄 Built-in support for await using via Symbol.asyncDispose
• 🧠 Works with navigator.locks or any custom LockManager (great for testing)

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Installation

npm install disposable-lock
# or
pnpm add disposable-lock

Quick Start

import { lock } from "disposable-lock";

async function main() {
  const { request } = lock("user-data");

  // --- Standard lock acquisition ---
  const acquired = await request({ mode: "exclusive" });

  if (acquired) {
    console.log(`✅ Lock acquired: ${acquired.name}`);
    await doSomething();
    await acquired.release();
  }

  // --- ifAvailable: true ---
  const maybeLock = await request({ ifAvailable: true });
  if (maybeLock) {
    console.log(`✅ Lock acquired (ifAvailable): ${maybeLock.name}`);
    await doSomething();
    await maybeLock.release();
  } else {
    console.log("⚠️ Lock not available (ifAvailable: true), skipping critical section");
  }
}

Using await using for automatic cleanup

import { lock } from "disposable-lock";

async function autoRelease() {
  const cacheLock = lock("cache-update");

  // --- Standard await using ---
  await using acquired = await cacheLock.request();
  if (acquired) {
    console.log("Lock acquired, performing critical section...");
    await doSomething();
  }

  // --- await using with ifAvailable: true ---
  await using maybeLock = await cacheLock.request({ ifAvailable: true });
  if (maybeLock) {
    console.log("Lock acquired (ifAvailable), performing critical section...");
    await doSomething();
  } else {
    console.log("Lock not available (ifAvailable: true), safe to skip");
  }
}

Key Points

• request() returns a ReleasableLock when successful, or null if the lock could not be obtained
• Wrapping with await using ensures automatic release at the end of the block
• ifAvailable: true attempts to acquire the lock but immediately returns null if unavailable

API

lock(name: string, options?: { locks?: LockManager })

Creates a lock handler bound to the given name.

Returns an object with:

Method	Description
request(options?: LockOptions)	Request a lock. Returns a ReleasableLock or a null.
query()	Query the current state (held and pending locks) for this name.

Throws if navigator.locks is unavailable and no custom LockManager is provided.

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ReleasableLock

Represents a successfully acquired lock.

Property / Method	Type	Description
name	string	Lock name
mode	"exclusive" | "shared"	Lock mode
release()	() => Promise<boolean>	Releases the lock
[Symbol.asyncDispose]()	() => Promise<void>	Enables await using syntax

Querying lock state

const userLock = lock("user-data");
const state = await userLock.query();

if (state.held) {
  console.log("Currently held by:", state.held.map(x => x.clientId));
}
if (state.pending) {
  console.log("Pending requests:", state.pending.length);
}

Testing with a custom LockManager

When running in Node.js or a test environment where navigator.locks is not available, you can provide your own LockManager instance:

import { lock } from "disposable-lock";
import { createMockLockManager } from "./test-utils"; // your mock

const locks = createMockLockManager();
const fileLock = lock("file-write", { locks });

Motivation

The Web Locks API provides powerful coordination primitives in browsers, but its callback-based API can be cumbersome. disposable-lock offers a clean, composable Promise interface and modern async dispose support — perfect for structured concurrency and testable code.

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MIT © juner