LedgerHardwareWallet.txt

import Web3 from "web3";
import createLedgerSubprovider from "@ledgerhq/web3-subprovider";
import TransportU2F from "@ledgerhq/hw-transport-u2f";
import ProviderEngine from "web3-provider-engine";
import RpcSubprovider from "web3-provider-engine/subproviders/rpc";

const contract_address = "The contract address goes here";
const abi = [];

let my_web3;
let account;
const rpcUrl = "https://ropsten.infura.io";
let contract;
window.addEventListener('load', () => {
  const use_ledger = location.search.indexOf("ledger=true") >= 0;

  if(use_ledger)
  {
    const engine = new ProviderEngine();
    const getTransport = () => TransportU2F.create();
    const ledger = createLedgerSubprovider(getTransport, {
      networkId: 3, // 3 == Ropsten testnet
    });
    engine.addProvider(ledger);
    engine.addProvider(new RpcSubprovider({ rpcUrl }));
    engine.start();
    my_web3 = new Web3(engine); 
  } else if(typeof(web3) === 'undefined') {
    my_web3 = new Web3(new Web3.providers.HttpProvider(rpcUrl));
  } else {
    my_web3 = new Web3(web3.currentProvider);    
  }
  contract = new my_web3.eth.Contract(abi, contract_address);
  my_web3.eth.getAccounts((error, result) => {
    if(error) {
      console.log(error);
    } else if(result.length == 0) {
      console.log("You are not logged in");
    } else {
      account = result[0];
      contract.options.from = account;
    }
  }).catch((error) => {
    console.log("Error: " + error);
  });
  contract.methods.message().call((error, result) => {
      if(error) {
          return console.log(error);
      }
      $('#message').text(result);
  }).catch((error) => {
    console.log("Error: " + error);
  });

  $('#set_message').click(setMessage);
});

function setMessage() {
  let message = $('#new_message').val();
  contract.methods.setMessage(message).send(
    {gasPrice: my_web3.utils.toWei("4.1", 'Gwei')}, 
    (error, result) => {
        if(error) {
            return console.log(error);
        }
        console.log("txhash: " + result); 
    }
  ).catch((error) => {
    console.log("Error: " + error);
  });
}