Hedera Hashgraph Javascript/Typescript SDK

The Javascript/Typescript SDK for interacting with Hedera Hashgraph: the official distributed consensus platform built using the hashgraph consensus algorithm for fast, fair and secure transactions. Hedera enables and empowers developers to build an entirely new class of decentralized applications.

Usage

This SDK supports both running in the browser (with Webpack) and in Node.

(Code examples using await assume an async context.)

Installation

# with NPM
$ npm install --save @hashgraph/sdk
# with Yarn
$ yarn add @hashgraph/sdk

Creating a client

import {Client} from "@hashgraph/sdk";

const client = new Client({ 
    // this key defaults to this url, a public free proxy to the Hedera public testnet
    // generously hosted by MyHederaWallet.com
    network: { "https://grpc-web.myhederawallet.com": "0.0.3" },
    operator: {
        // the account which signs transactions and query payments by default
        account: { shard: 0, realm: 0, account: ___ },
        // the private key used to sign the transactions, either encoded as a string
        // or as an `Ed25519PrivateKey` type 
        privateKey: "..."
    },
});

Checking your balance

console.log('current account balance:', await client.getAccountBalance());

Sending a transfer

// the amount parameter can either be a `number` or a bignumber.js type
new CryptoTransferTransaction()
    .addSender({ shard: 0, realm: 0, account: ___ }, 10_000_000)
    .addRecipient({ shard: 0, realm: 0, account: ___ }, 10_000_000)
    .build(client)
    .execute(client);

Creating a new Account

import { Ed25519PrivateKey } from "@hashgraph/sdk";

const privateKey = await Ed25519PrivateKey.generate();
const publicKey = privateKey.publicKey;

const tx = new AccountCreateTransaction()
    .setKey(privateKey.publicKey)
    .setInitialBalance(0)
    .build(client);

await tx.execute(client);
const receipt = await tx.getReceipt(client);
const newAccount = receipt.accountId;

console.log('new account: ', newAccount, 'public key: ', publicKey.toString(), ' private key: ', privateKey.toString());

Development

To build the SDK from source, you must have the official Protobufs compiler, protoc, installed:

Arch (with Pikaur):

# Pacman
$ sudo pacman -S protobuf
# with Pikaur
$ pikaur -S protobuf

Ubuntu/Debian:

# libprotobuf-dev contains the Protobuf definitions for standard types
$ sudo apt-get install protobuf-compiler libprotobuf-dev

Mac OSX:

# Homebrew
$ brew install protobuf

Hosting your own Envoy Proxy

This SDK talks to Hedera Hashgraph through the gRPC-Web protocol which allows it to function in a browser. By default, the SDK points to a public free proxy that connects through to 0.testnet.hedera.com:50211. If you want to change this endpoint or simply host your own proxy, a script to easily start an Envoy proxy in Docker is provided:

# this script assumes that `envoy.yaml` is in the current working directory
$ ./scripts/start-envoy.sh

You can modify the endpoint to connect to in envoy.yaml.

Updating Protobufs

If the protobuf files are ever found to be out of sync, you can update them easily as follows:

$ ./scripts/update-protos.sh

This will temporarily clone https://github.com/hashgraph/hedera-protobuf and copy the protobufs from there.

NOTE: some Protobufs have to be manually patched

In most places where sint64 or uint64 is used in the protobufs, they have to be patched to annotate these fields as [jstype=JS_STRING] or the Protobufs-JS library will try to decode them as JS number types which can only represent exact integers in the range [-2^53, 2^53 - 1].

(This is only really necessary for values which may conceivably fall outside that range, like tinybar amounts. We're assuming for now that shard/realm/entity numbers will not exceed this range for a very long time.)

Since update-protos.sh will inevitably clobber these modifications, it has the feature of automatically applying patches defined in patches to the files in src/protos after overwriting. These patch files have the original filename and extension and then an additional .patch extension, e.g. src/protos/CryptoCreate.proto has a patch file at the path patches/CryptoCreate.proto.patch.

If you find a new file needs to be modified, you can make the modification in src/protos, and before committing it, run the following:

$ git diff src/proto/[proto file] > patches/[proto file].patch 

Then check-in the .patch file that was created and commit it as well as the change to the Protobuf file. Your modification will then be preserved across update-protos.sh runs.

If you need to add modifications to an existing patch file, you need to recreate the patch file that contains both existing modifications as well as new modifications. If you run into this and don't know how to proceed, don't be afraid to ask for help.

DISCLAIMER

This project is actively under development and not recommended for production use. Join the Hedera discord for the latest updates and announcements.

LICENSE

Copyright 2019 Hedera Hashgraph LLC

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.