dexie-worker

dexie-worker is an extension package for Dexie.js that enables Dexie to work seamlessly in a Web Worker environment, allowing for smoother handling of IndexedDB operations without blocking the main thread. This package provides an easy way to enhance your Dexie-based applications with Web Worker support, along with a convenient React hook for live query subscriptions.

Features

• Web Worker Integration: Run Dexie.js in a Web Worker to improve app performance and responsiveness.
• React Hook Support: Use useLiveQuery to fetch and subscribe to live data changes, optimized for a Web Worker context.

Installation

Install the package via npm:

npm install dexie-worker

Usage

To get started with dexie-worker, import getWebWorkerDB to set up Dexie in a Web Worker context and enjoy a non-blocking database experience.

Basic Setup

1. Define Your Dexie Database: Create a Dexie subclass or use a function-based approach to define your database schema.
2. Initialize with Web Worker: Use getWebWorkerDB to enable Web Worker functionality for your Dexie instance.

Example 1: Function-Based Dexie Database

Here’s a basic setup for integrating dexie-worker in your Dexie project using a function-based approach:

import Dexie from "dexie";
import { getWebWorkerDB } from "dexie-worker";

// Define a function-based Dexie instance
function createDatabase() {
  const db = new Dexie("MyDatabase");
  db.version(1).stores({
    products: "++id, name"
  });
  return db;
}

// Initialize with Web Worker DB insance
const db = getWebWorkerDB(createDatabase());

Now, db will run on a separate thread, keeping your main UI thread responsive and free from database-related tasks.

Example 2: Class-Based Dexie Database

Alternatively, you can integrate dexie-worker in your Dexie project with a class-based approach.

import Dexie from "dexie";
import { getWebWorkerDB } from "dexie-worker";

// Define your Dexie subclass
class MyDatabase extends Dexie {
  constructor() {
    super("MyDatabase");
    this.version(1).stores({
      users: "++id, name"
    });
  }
}

// Initialize with Web Worker support
const db = getWebWorkerDB(new MyDatabase(), {
  dexieVersion: 'latest' // Use 'latest' or a specific version like '4.0.9 - it should be accessible from the url: https://cdn.jsdelivr.net/npm/dexie@{YOUR VERSION}/dist/dexie.min.js
});

With this setup, you're free to use a function-based approach to organize and create multiple Dexie instances or handle conditional setups within your application.

React Hook: useLiveQuery

dexie-worker also provides a convenient useLiveQuery hook for React applications, which allows you to subscribe to live query updates from the database.

⚠️ Warning: Unlike the default usage in dexie-react-hooks, you'll need to pass the db instance within the callback function.

Usage Example

import { useLiveQuery } from "dexie-worker";

// IMPORTANT: use "db" returned from the callback function
const userDetails = useLiveQuery((db) => db.users.get({ id: 1 }));

// userDetails will automatically update when data changes

By wrapping db in the callback function, useLiveQuery efficiently maintains real-time updates in your React components, utilizing the Web Worker's isolated environment.

Custom Live Queries

For advanced usage, dexie-worker exports the liveQuery function, allowing you to create your own custom live queries outside of React components.

Example of a Custom Live Query

import { liveQuery } from "dexie-worker";

// Create a custom live query
const userLiveData = liveQuery(() => db.users.where("age").above(18).toArray());

// Subscription to the live query
userLiveData.subscribe({
  next: (data) => console.log("User data updated:", data),
  error: (error) => console.error("Live query error:", error),
});

Content Security Policies

This library uses code injection to execute the web worker, which may not comply with Content Security Policy (CSP) if your website uses one. To ensure CSP compliance, please follow the Generate Web Worker File section.

Generate Web Worker File

To generate a web worker file, execute the following

generate-dexie-worker

This command generates a web worker file based on your project configuration. The file needs to be placed in a publicly accessible location (e.g. http://localhost/dexieWorker.js)

To initialize the Dexie worker with the generated file:

const db = getWebWorkerDB(dexieDb, {
  workerUrl: '/dexieWorker.js' // the path can be different based on your environment
});

This will no longer use code injection.

Custom Operations

You can create custom operations to run within the web worker to improve performance and extend support to cases that are otherwise unsupported due to limitations in communicating with the web worker, such as the inability to pass callbacks (e.g., with methods like each). To get started, follow these steps:

1. Create a dexieOperations.js(or .ts) file with your custom operations:

import Dexie from "dexie";
import map from "lodash.map"; // you can use eternal libraries

export default {
  async runBulkOperationInWorkerExample(dexie: Dexie, arg1: any, arg2: any) {
    const oldUsers = await dexie.users.toArray();

    const newUsers = map(oldUsers, user => ({
      ...user,
      isActive: true,
    }));

    await dexie.transaction('rw', dexie.usersV2, async () => {
      await dexie.usersV2.bulkPut(newUsers);
    });
    
    return 'A seralizable result' // e.g Objects, Arrays, Strings, etc. To learn more about not supported types refer to https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm#things_that_dont_work_with_structured_clone
  },
  // ...other methods
}

2. Generate the web worker file:

generate-dexie-worker ./path/to/dexieOperations.js

Note: The command automatically detects your Dexie version from package.json, but you can specify a version manually:

npx generate-dexie-worker ./path/to/dexieOperations.js "3.2.2"

3. Place the generated file in a publicly accessible location(e.g. http://localhost/dexieWorker.js)
4. initialize the dexie worker with the following options:

const db = getWebWorkerDB(dexieDb, {
  workerUrl: '/dexieWorker.js' // the path can be different based on your environment
});

5. Call your custom operations:

const result = db.operation('runBulkOperationInWorkerExample', arg1, arg2)

API

getWebWorkerDB(dbInstance)

• Description: Converts a Dexie instance to run in a Web Worker.
• Parameters:
  • dbInstance: An instance of your Dexie subclass or function-based instance.
• Returns: A Web Worker-enabled Dexie instance.

useLiveQuery(queryCallback)

• Description: React hook for live queries on Dexie. Optimized for Web Worker integration.
• Parameters:
  • queryCallback: A callback function to execute the query, taking db as an argument.
• Returns: The result of the query, updating automatically with data changes.

liveQuery(queryCallback)

• Description: A function for setting up custom live queries with automatic updates.
• Parameters:
  • queryCallback: A callback function defining the query logic.
• Returns: A subscribable that emits updates when the query result changes.

Compatibility

• Dexie.js v3.0+ and v4.0+
• React v16.8+ (if using useLiveQuery)

License

MIT

Contribution

Feel free to contribute to the project by creating issues or pull requests. Contributions, bug reports, and feature requests are welcome!