Blockchain Development Programming Tutorials, Guides & Best Practices

Both crypto.randomBytes and ethers.randomBytes generate cryptographically secure random bytes, meaning the bytes are suitable for use in cryptographic applications such as key generation, encryption, and other security-sensitive operations.

• Use crypto.randomBytes when:
• You are building Node.js applications without blockchain-specific functionality.
• You want to avoid adding external dependencies.
• Use ethers.randomBytes when:
• You are developing Ethereum-related applications and already have ethers.js in your project.
• You want the flexibility of generating random bytes with minimal configuration, defaulting to 32 bytes for Ethereum addresses or private keys.

In this step, we will use Ethers.js to query the balance of an ERC-20 token for a specific Ethereum address.

const ethers = require('ethers');

// Replace with your Infura or other Ethereum node provider URL
const provider = new ethers.JsonRpcProvider('https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID');

// Replace with the ERC-20 token contract address (e.g., USDT, DAI)
const contractAddress = '0xTokenContractAddress';

// Replace with the wallet address you want to query
const walletAddress = '0xYourEthereumAddress';

// ERC-20 token ABI (just the balanceOf function)
const abi = [
    'function balanceOf(address owner) view returns (uint256)'
];

// Create a contract instance
const contract = new ethers.Contract(contractAddress, abi, provider);

async function getTokenBalance() {
    try {
        // Query the balance
        const balance = await contract.balanceOf(walletAddress);

        // Convert balance to a human-readable format (tokens usually have 18 decimals)
        const formattedBalance = ethers.utils.formatUnits(balance, 18);

        console.log(`Token Balance: ${formattedBalance}`);
    } catch (error) {
        console.error('Error fetching token balance:', error);
    }
}

// Call the function to get the token balance
getTokenBalance();

const ethers = require('ethers');

// Replace with your Infura Project ID
const infuraProvider = new ethers.JsonRpcProvider('https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID');

// Replace with your wallet's private key
const privateKey = 'YOUR_PRIVATE_KEY';

// Create a wallet instance and connect it to Infura
const wallet = new ethers.Wallet(privateKey, infuraProvider);

// Replace with the recipient's Ethereum address
const recipientAddress = '0xRecipientEthereumAddress';

// Amount to send (in Ether)
const amountInEther = '0.01';

async function sendTransaction() {
  try {
    const tx = {
      to: recipientAddress,
      value: ethers.utils.parseEther(amountInEther),
      gasLimit: 21000, // Gas limit for a basic transaction
      gasPrice: await infuraProvider.getGasPrice() // Get current gas price from Infura
    };

    // Send the transaction
    const transaction = await wallet.sendTransaction(tx);
    console.log('Transaction Hash:', transaction.hash);

    // Wait for the transaction to be mined
    const receipt = await transaction.wait();
    console.log('Transaction Confirmed:', receipt);
  } catch (error) {
    console.error('Error sending transaction:', error);
  }
}

sendTransaction();

• API: This script uses Infura’s node access and Ethers.js to send Ether in real-time.
• Use Case: Essential for dApps, wallets, or any application needing to send transactions or interact with the blockchain live.

const ethers = require('ethers');

// Replace with your Infura Project ID
const infuraProvider = new ethers.JsonRpcProvider('https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID');

// Replace with your private key
const privateKey = 'YOUR_PRIVATE_KEY';

// Create a wallet instance and connect it to Infura
const wallet = new ethers.Wallet(privateKey, infuraProvider);

// Contract bytecode and ABI
const bytecode = '0xYourContractBytecode';
const abi = [
    // Your contract ABI here
];

async function deployContract() {
    try {
        // Create a ContractFactory to deploy the contract
        const factory = new ethers.ContractFactory(abi, bytecode, wallet);

        // Deploy the contract
        const contract = await factory.deploy();

        // Wait for the contract to be mined
        console.log('Contract deployed at address:', contract.address);
        await contract.deployTransaction.wait();
    } catch (error) {
        console.error('Error deploying contract:', error);
    }
}

// Call the function to deploy the contract
deployContract();

• Bytecode and ABI: The contract bytecode is the compiled contract, and the ABI defines the contract’s interface. You need both to deploy the contract.
• The contract will be deployed using your Infura provider and wallet, and once mined, it will return the deployed contract address.

• Replace 'YOUR_ETHERSCAN_API_KEY' with your Etherscan API key.
• Replace '0xYourEthereumAddress' with the address you want to query.
• Replace '0xYourTokenContractAddress' with the ERC-20 token's contract address (e.g., USDT or DAI token contract).
• This script queries the ERC-20 token balance for a specific Ethereum address.

   https://api.etherscan.io/api?module=account&action=txlist&address=0xYourEthereumAddress&startblock=0&endblock=99999999&sort=asc&apikey=YOUR_API_KEY