ylv-io

// web3 has to be injected/present
if (web3js) {
  if (web3js.eth.accounts.length) {
    // if not locked, get account
    const account = web3js.eth.accounts[0];
    // updates UI, state, pull data
  } else {
    // locked. update UI. Ask user to unlock.
  }
}

ylv-io

if (web3js) {
  switch (web3js.version.network) {
    case '1':
      console.log('This is mainnet');
      break;
    case '2':
      console.log('This is the deprecated Morden test network.');
      break;
    case '3':
      console.log('This is the ropsten test network.');

ylv-io

const getAccount = () => {
  // check if web3 present
  if (web3js) {
    // return default account
    return web3js.eth.accounts[0];
  }
  return undefined;
};

ylv-io

web3js.eth.getBalance(getAccount(), (err, balance) => {
  const balanceInEth = web3js.fromWei(balance, 'ether');
  console.log(`balance ${balanceInEth} ether`);
});

ylv-io

let account = getAccount();
let accountInterval = setInterval(() => {
  if (getAccount() !== account) {
    account = getAccount();
    // update UI, state, pull data
    updateEverything();
  }
}, 1000);

ylv-io

let account = getAccount();
let accountInterval = setInterval(() => {
  if (getAccount() !== account) {
    account = getAccount();
    if (account === undefined) {
      // if account changed to undefined, that means metamask is now locked
      updateEverything();
    } else {
      // if account is not undefined, that means metamask is now unlocked
      updateEverything();

ylv-io

try {
  const account = getAccount();
  const hash = await yourContractInstance.yourMethod.sendTransaction(arg1, arg2, {
      from: account,
      // if payable, specify value
      // value: web3js.toWei(value, 'ether')
    });
  // update progress UI
  setSubmitting(false);
  // reset transaction related form, if any

ylv-io

const getTransactionReceipt = async (hash) => {
  let receipt = null;
  while (receipt === null) {
    // we are going to check every second if transation is mined or not, once it is mined we'll leave the loop
    receipt = await getTransactionReceiptPromise(hash);
    await wait(1000);
  }
  return receipt;
};

ylv-io

// both web3 and your contract have be defined
if(web3js && contract)
{
    const yourEvent = contract.YourEventName();
    yourEvent.watch(function(error, result) {

      if (!error) {
        
//         Callback return
//         Object - An event object as follows:

ylv-io

pragma solidity ^0.4.24;


/**
 * @title FiatTokenProxy
 * @dev This contract proxies FiatToken calls and enables FiatToken upgrades
*/ 
contract FiatTokenProxy is AdminUpgradeabilityProxy {
    constructor(address _implementation) public AdminUpgradeabilityProxy(_implementation) {
    }