Javascript libraries to interact with the Winding Tree contracts

Usage no npm install needed!

<script type="module">
  import afklblockchainWtJsLibs from 'https://cdn.skypack.dev/@afklblockchain/wt-js-libs';


Winding Tree Javascript Libraries for Hotels

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A JS interface to WindingTree's Ethereum smart-contracts for Hotels.


npm install @afklblockchain/wt-js-libs
# or
git clone https://github.com/windingtree/wt-js-libs
nvm install
npm install


For more examples, see test/usage.spec.js file. The public interface of this library should always be the same regardless of what kind of implementation is used under the hood.

// Winding Tree backed by a local Ethereum node.
// You need to deploy the index and the hotel first. See test/utils/migrations
// for inspiration.
import WTLibs from '@afklblockchain/wt-js-libs';
import InMemoryAdapter from '@windingtree/off-chain-adapter-in-memory';

const libs = WTLibs.createInstance({
  dataModelOptions: {
    provider: 'http://localhost:8545',
  offChainDataOptions: {
    adapters: {
      // This is how you plug-in any off-chain data adapter you want.
      'in-memory': {
        options: {
          // some: options
        create: (options) => {
          return new InMemoryAdapter(options);
const index = libs.getWTIndex('0x...');
const hotel = await index.getHotel('0x...');

// You can get all the off-chain data at once
// This approach might be a little slow as all off-chain data gets downloaded
const plainHotel = await hotel.toPlainObject();
// You get a synced plain javascript object you can traverse in any way you want
const hotelName2 = plainHotel.dataUri.contents.descriptionUri.contents.name;

// OR you can be picky but faster

// Accessing off-chain data - the entry point url is actually stored on chain
const dataIndex = await hotel.dataIndex;
const hotelDataIndexUrl = dataIndex.ref;
// This data is fetched from some off-chain storage
const dataIndexContents = await dataIndex.contents;
const hotelDescriptionDocument = await dataIndexContents.descriptionUri.contents;
// This data is fetched from another off-chain document
const hotelName = hotelDescriptionDocument.name;

// How about creating a hotel?
wallet = libs.createWallet({/*...Your wallet in a JSON format..*/});
try {
  const { hotel, transactionData, eventCallbacks } = await index.addHotel({
    manager: wallet.getAddress(),
    dataUri: 'https://example.com/my-hotel-data.json',
  const result = await wallet.signAndSendTransaction(transactionData, eventCallbacks);
  // After the transaction is confirmed, one of the callbacks
  // will set the address of the hotel.
  const newHotelAddress = hotel.address;
} finally {


The current documentation can be rendered by running npm run docs

Off-chain data adapters

Existing implementations

  • In memory - Example basic implementation which is not very useful, but should be enough for quick hacking or testing
  • Swarm - Uses Ethereum Swarm for off-chain storage.
  • HTTPS - Retrieves data from arbitrary HTTPS locations.

Developing your own off-chain data adapter

For insipiration, you can have a look at in-memory adapter, if you'd like to create it all by yourself, here's what you need.

  1. Your package has to implement a simple interface that provides ways to store, update and retrieve data.
  2. You can also choose how your plugin is instantiated and whether you need any initialization options. These will be passed whenever an instance is created.
  3. Off Chain data adapters are used in two places
    1. StoragePointer - The adapter is used to download off-chain data in there
    2. OffChainDataClient - It is responsible for proper instantiation of all off-chain data adapters.

The interface is subject to change as we go along and find out what other types of storages might require - be it a signature verification, data signing and other non-common utilities. The only actual method used in the wt-js-libs internals is download right now.


To run unit tests, run npm test.