send-eth-by-private-key.js

// Its your address with some Ethereum balance
const fromAddress = '0x062c6ebe692d0E31B79Eff9532F835bF0dbc1f45';
// Its private key of your address
const privateKey = '0x3a622a1c7504b6be1b77a6b12ac1438d50ada2906bd871b15aefd627aec872aa';

// Its your friend's wallet address
const toAddress = '0x6122a161c39907502B8BB4636215374389B95c6f';

// Its amount of eth, which you want to send to friend
const ethAmount = 0.01;
// Convert it to wei https://etherconverter.online/
const weiAmount = ethAmount * (10 ** 18);

// Ethereum node, where do you send the transaction
const rpcServer = 'http://127.0.0.1:8545';
const Web3 = require("web3");
const web3 = new Web3(new Web3.providers.HttpProvider(rpcServer));

// First need to know gasPrice of the current network
web3.eth.getGasPrice().then(async (gasPrice) {
  gasPrice = parseInt(gasPrice) || '1000000000';
  
  // Second - get nonce of address(number of new transaction)
  const txCount = await web3.eth.getTransactionCount(fromAddress);
  let nonce = `${txCount++}`;

  // Convert nonce, ethAmount, gasPrice and gasLimit to hex
  const nonceHex = web3.utils.numberToHex(nonce);
  const weiAmountHex = web3.utils.toHex(weiAmount);
  const gasPriceHex = web3.utils.toHex(gasPrice);
  const gasLimitHex = web3.utils.toHex("3000000");

  var transactionOptions = {
      nonce: nonceHex,
      gasPrice: gasPriceHex,
      gasLimit: gasLimitHex,
      from: fromAddress,
      to: toAddress,
      value: weiAmountHex
  };

  // Create Transaction instance
  var tx = new Tx(transactionOptions);
  tx.sign(Buffer.from(config.private_key, 'hex'));

  var stx = tx.serialize();

  // Send transaction to rpc server
  web3.eth.sendSignedTransaction('0x' + stx.toString('hex'), (err, hash) => {
      if (err) { console.log(err); return; }
      console.log('sent tx: ' + hash);
  });
});