Check links below for the JavaScript SDK:

• Codebase

• NPM Packages

• Draft Documentation

Introduction

This guide walks through the process of using web3.js to manually sign and send a transaction to a Harmony network. For this example, we will use Node.js and straightforward JavaScript code.

For this guide we will use Harmony Testnet Network.

Install Dependencies

Next, we can create a directory to store all our relevant files by running:

mkdir transaction && cd transaction/

And create a simple package.json file:

npm init --yes

With the package.json file created, we can then install the web3.js package by executing:

npm install web3
npm install 'bn.js'

To verify the installed version of web3.js, you can use the ls command:

npm ls web3

As of the writing of this guide, the version used was 1.3.0.

Sending Transaction

For our example, we only need a single JavaScript file (arbitrarily named transaction.js, which you can find here) to create and send the transaction, which we will run using the node command in the terminal. The script will transfer 1 ONE from the genesis account to another address. For simplicity, the file is divided into three sections: variable definition, create transaction, and deploy transaction.

We need to set a couple of values in the variable definitions:

1. Create our Web3 constructor (Web3).

2. Define the HMY_PRIVATE_KEY variable as the private key of your ONE wallet, what is used to sign the transactions.

3. Create a local Web3 instance and set the provider to connect to Testnet Harmony network.

Setup Account

const Web3 = require('web3');
const BN = require('bn.js');

HMY_PRIVATE_KEY = 'YOUR_PRIVATE_KEY';
HMY_TESTNET_RPC_URL = 'https://api.s0.b.hmny.io';

const web3 = new Web3(HMY_TESTNET_RPC_URL);

let hmyMasterAccount = web3.eth.accounts.privateKeyToAccount(HMY_PRIVATE_KEY);
web3.eth.accounts.wallet.add(hmyMasterAccount);
web3.eth.defaultAccount = hmyMasterAccount.address

const myAddress = web3.eth.defaultAccount;
console.log('My address: ', myAddress);

Check Account Balance

const balance = await web3.eth.getBalance(myAddress);
console.log('My balance: ', balance / 1e18);

Create new account on which we will send tokens

const newAccount = web3.eth.accounts.create();
console.log('New account created: ', newAccount.address);

Sending a Transaction

const gasPrice = new BN(await web3.eth.getGasPrice()).mul(new BN(1));
const gasLimit = 6721900;

const value = 1 * 1e18; // 1 ONE

const from = web3.eth.defaultAccount;
const to = newAccount.address; // account was created on prev step

const result = await web3.eth
      .sendTransaction({ from, to, value, gasPrice, gasLimit })
      .on('error', console.error);
      
console.log(`Send tx: ${result.transactionHash} result: `, result.status);

const newAddrBalance = await web3.eth.getBalance(newAccount.address);
console.log('New account balance: ', newAddrBalance / 1e18);

Full code samples can be found here.

Check links below for the Go CLI:

• Code

• Packages

• Documentation

Introduction

Web3.js is a set of libraries that allow developers to interact with Ethereum nodes using HTTP, IPC or WebSocket protocols. Harmony has an Ethereum-like API available that is fully compatible with Ethereum-style JSON RPC invocations. Therefore, developers can leverage this compatibility and use the web3.js library to interact with a Harmony node as if they were doing so on Ethereum.

Setup Web3.js with Harmony

To get started with the web3.js library, we first need to install it using the following command:

npm install web3

Once done, the simplest setup to start using the library and its methods is the following:

const Web3 = require('web3');

//Create web3 instance
const web3 = new Web3(HMY_RPC_URL);

Depending on which network you want to connect to, you can set the HMY_RPC_URL to the following values:

For Mainnet:

HMY_RPC_URL = https://api.s0.t.hmny.io

For Testnet:

HMY_RPC_URL = https://api.s0.b.hmny.io

Tutorials

In the case that you are interested in a more detailed step-by-step guide, you can go to our specific tutorials on using web3.js on a Harmony:

The steps can also be adapted to deploy on the Harmony Testnet, by using the correct RPC_URL as mentioned before.

Repo:

Example: How to use provider to query Harmony chain

Check links below for the Python SDK:

Introduction

This guide walks through the process of using to get last block and get last transaction.

For this example, we will use Node.js and straightforward JavaScript code.

Get Block Number

Get Last Transaction

Check links below for the Java SDK: