[Ethereum] TypeError: Cannot read property ‘then’ of undefined

reactsolidityweb3js

I am having an error with Web3. After going through all possibilities I decided to post a question hoping for someone with a solution.

The error I keep getting is:

TypeError: Cannot read property 'then' of undefined

web3.eth.getAccounts().then(accounts => {
   web3.eth.getBalance(accounts[0]).then(balance => {
      console.log(balance);
    }
}

Note: this exact same code is running fine on two other servers. I do have the exact same versions of Truffle, React..etc as the other two.

Any solutions will be appreciated! Thanks in advance.

Best Answer

have you tried to add a catch in order to output the stacktrace of your error ?

Just add at the end of your promise chain : then(account => {...}).catch( err => { console.log(err); }

You'll then be able to see in the console the stacktrace of the error and distinguish if it is accounts or accounts[0] which is undefined.

If it is accounts[0], ensure your web3 instance is connected. If is is the whole accounts object, ensure you use Web3.js v1.x.x and not v.0.2.x

Related Solutions

[Ethereum] TypeError: Cannot read property ‘abiDefinition’ of undefined

The method eth_compileSolidity which web3.eth.compile.solidity relies on is deprecated and does not exist nor is available anymore.

An alternative is to compile using solc:

solc --abi Calc.sol -o ./build

which generates the ABI file:

├── Calc.sol
├── build
│   └── Calc.abi

Or compiling with solc in node.js:

const fs = require('fs')
const solc = require('solc')

const input = fs.readFileSync('Calc.sol')
const output = solc.compile(input.toString(), 1)
const abi = output.contracts[':Calc'].interface

console.log(abi)

Web3 Integration – How to Import Web3 into a React Project

It sounds confusing and basing on the version of web3 you have the syntax is different. According to the error you got at the first place seems like you are using web3 1.0. However the instance code is for the version 0.2.x.x

Just to clarify, this is how your code will look like in case you're using web3 1.0

import Web3 from 'web3';

const web3 = new Web3(Web3.givenProvider || "http://localhost:8545");
web3.eth.getAccounts().then(console.log);

So basically you create an instance of web3 with the givenProvider (in case you're using metamask or mist) or with the local. Then you get your accounts.

In case you're using the old version of web3 the code is slightly different:

import Web3 from 'web3';

let web3 = null;
if (typeof web3 !== 'undefined') {
  web3 = new Web3(web3.currentProvider);
} else {
  // set the provider you want from Web3.providers
  web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
}

web3.eth.getAccounts(callback(error, result){ console.log(result) })

Best Answer

Related Solutions

[Ethereum] TypeError: Cannot read property ‘abiDefinition’ of undefined

Web3 Integration – How to Import Web3 into a React Project

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