how can I prevent web3 function calls printing out the Promise; I only want the actual value printed out

Question

I'm using node.js to execute a simple JavaScript script that tests access to the rinkeby blockchain using an infura endpoint. specifically, it is checking the balance of my address.

In the code if I invoke:

console.log(web3.eth.getBalance(address));

it only returns the Promise i.e.

Promise {
  _bitField: 0,
  _fulfillmentHandler0: undefined,
  _rejectionHandler0: undefined,
  _promise0: undefined,
  _receiver0: undefined }

If on the other hand I call:

console.log(web3.eth.getBalance(address, function (error, result) { }));

it returns both the Promise and the address balance i.e..

Promise {
  _bitField: 0,
  _fulfillmentHandler0: undefined,
  _rejectionHandler0: undefined,
  _promise0: undefined,
  _receiver0: undefined }
18750000000000000000

I don't really understand why it prints out the Promise at all. I simply want it to return the value only i.e. 18750000000000000000

How can I achieve this and do I really need to specify the function (error, result) { } optional parameter to all the web3 function calls just to get it to return me the data I need?

thanks

Answer 1

try with something along the lines of:

const get_eth_balance = async (web3, account) => {

  const balance = await web3.eth.getBalance(account);

  return balance;
};

get_eth_balance(web3, account);

The main keywords here being the async/await which make the code look much saner than it would by using callbacks.

Answer 2

If I remember correctly the current web3 version (v1.0) doesn't support synchronous operations. If you want synchronous functions (without promises or async/await) you could install the previous version by doing the following:

npm install [email protected]

const Web3 = require('web3')
const web3 = new Web3(new Web3.providers.HttpProvider('https://rinkeby.infura.io'))
const address = '0x966e42aA4E7368818517a93656362C30d8E4d5fE'
const balance = web3.eth.getBalance(address)
console.log(balance.toNumber())