[Ethereum] Deploying a contract with Web3.js

Often the contract itself is going to need to store the address for future use. So just store the address in the contract as an attribute, and retrieve it from outside the contract using the usual methods (e.g. call to the default getter ABI if you declare it public scope), after the transaction has been completed: (note, untested pseudo code, but I've done similar stuff a few times)

contract ObjectFactory {
    Object public theObj;

    function createObject(string name) returns (address objectAddress) {
        theObj = address(new Object(name));
        return theObj;
    }
}

I've used this scripts to deploy a contract using web3 v1.0-beta24

const Web3 = require('web3');
const web3 = new Web3('http://127.0.0.1:8545');

const ownerAddress = "0x....";
const contractAbi = [{"constant":false.... }];
const contractCode = "0x606060...";

const MyContract = new web3.eth.Contract(contractAbi);

MyContract.deploy({
  data: contractCode,
})
.send({
  from: ownerAddress,
  gas: 4000000,
  gasPrice: '30000000000000',
})
.then((instance) => {
  console.log(`Address: ${instance.options.address}`);
});

And this other script to send a message and make a query

const Web3 = require('web3');
const web3 = new Web3('http://127.0.0.1:8545');

const ownerAddress = "0x....";
const contractAbi = [{"constant":false.... }];
const contractCode = "0x606060...";
const contractAddress = "0x....";  // <----- previous script output

const myContract = new web3.eth.Contract(contractAbi, contractAddress);

const options = {
  from: ownerAddress,
  gas: 4000000,
  gasPrice: '30000000000000',
};

const message = web3.utils.asciiToHex('hola');

myContract.methods.sendMessage(message)
.send(options, (err, hash) => {
  if (err) {
    console.log(err);
  }
  console.log(`TxHash: ${hash}`);
})
.then((result) => {
  myContract.methods.getMessage().call()
  .then((result) => {
    console.log(web3.utils.hexToAscii(result));
  });
});

The sample contract I've used is very simple

pragma solidity ^0.4.18;

contract Echo {
    bytes32 public message;

    function sendMessage(bytes32 _message) public {
        message = _message;
    }

    function getMessage() view public returns (bytes32) {
        return message;
    }
}