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  • Introduction
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  1. Developers
  2. SDK
  3. Web3.js

Using Web3.js to Send Transactions on Harmony

PreviousWeb3.jsNextFind the last transaction

Last updated 3 years ago

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Introduction

This guide walks through the process of using 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'

We recommended to use for format values

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

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);

For our example, we only need a single JavaScript file (arbitrarily named transaction.js, which you can find ) 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.

Full code samples can be found

🏗️
web3.js
bn.js
here
here.