How to call contract functions using web3?

Question

I have deployed my contract in private blockchain, now I am calling functions using Nodejs and web3. Here, I want to transfer tokens for which I need to unlock my account from which I am transferring the tokens and then I want to check the balance of the account to which the tokens were transfered. Here, is the code:

var Web3 = require('web3');
var web3 = new Web3(new 
Web3.providers.HttpProvider("http://localhost:8545"));
var Personal = require('web3-eth-personal')
var personal = new Personal(Personal.givenProvider)

var ABI = {contract abi}
web3.eth.personal.unlockAccount("0xcc8d743....97278fe497ee90...", "password", 
60).then(
contract.methods.transfer('0x43a91c052B913299Dd4F47C91bB7d982D8A8632e', 
2).send({from:'0xCc8d743eB486bF38ED1197278Fe497eE90...', gas:210000})
.on("result", 
contract.methods.balanceOf('0x43a91c052B913299Dd4F47C91bB7d982D8A8632e')
.call((error, result)=>console.log(result))).on("error", function(error) 
{console.log(error);}))

But I am getting the balance of the account first which should be called after transfer function and for the transfer function I am getting the error saying 'need authentication'.

100000008
Error: Returned error: authentication needed: password or unlock

Answer 1

Use this code. It's all mentioned clearly in documentation, unlocking account and send transaction. You can also see how-to-call-my-contracts-function-using-sendtransaction

let isUnlocked = await web3.eth.personal.unlockAccount("0xcc8d743....97278fe497ee90...", "password", 
60)

if(isUnlocked){
  myContract.methods.myMethod(123).send({from: '0xcc8d743....97278fe497ee90...'}, (error, txHash) => {
    // handle the error here
    if(!err && txHash){
      myContract..methods.balanceOf('0xcc8d743....97278fe497ee90...', (err, balance) => {
        console.log('balance is', balance)
      })
    }
});

}

Using Callbacks

web3.eth.personal.unlockAccount('0x..', 'password', (unlocked) => {
  myContract.methods.myMethod(123).send({from: '0xcc8d743....97278fe497ee90...'}, (error, txHash) => {
    if(!err && txHash){
      myContract..methods.balanceOf('0xcc8d743....97278fe497ee90...', (err, balance) => {
        console.log('balance is', balance)
      })
    }
  });
})