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Retrieve the balance of an ERC-20 token

In this tutorial, using Web3.js, you'll retrieve the balance of an ERC-20 token in an account, using the account address and the token contract.

Prerequisites​

Steps​

1. Create a project directory​

Create a new directory for your project. This can be done from the command line:

mkdir retrieveBalance

Change into the new directory:

cd retrieveBalance

2. Install required packages​

Install the web3 package in the project directory:

npm install web3

3. Set up the script​

Create a file called retrieveBalance.js. At the top of file, add the following lines to import the web3.js library and connect to the Infura HTTPS endpoint:

const { Web3 } = require("web3")
const web3 = new Web3(
  new Web3.providers.HttpProvider("https://mainnet.infura.io/v3/<YOUR-API-KEY>")
)

Make sure to replace <YOUR-API-KEY> with your Infura API key.

4. Set the ABI​

You'll only use the balanceOf method, so you don’t need the entire ABI for ERC-20 smart contracts. In the retrieveBalance.js file, define the ABI for the balanceOf method by adding the following to the script:

const balanceOfABI = [
  {
    constant: true,
    inputs: [
      {
        name: "_owner",
        type: "address",
      },
    ],
    name: "balanceOf",
    outputs: [
      {
        name: "balance",
        type: "uint256",
      },
    ],
    payable: false,
    stateMutability: "view",
    type: "function",
  },
]

5. Select a token address​

To retrieve the balance of a token, you need the contract address of the token. You can find this in the tokens section of a block explorer such as Etherscan.

This example uses a DAI token contract. However, you can use any ERC-20 token contract address. Copy the token contract address you wish to use.

6. Request the token balance​

Define the addresses to use in the retrieveBalance.js script:

const tokenContract = "0x6b175474e89094c44da98b954eedeac495271d0f"
const tokenHolder = "0xf326e4de8f66a0bdc0970b79e0924e33c79f1915"

Define contract using web3.eth.Contract(), passing the balanceOfABI and the token contract address tokenContract as parameters:

const contract = new web3.eth.Contract(balanceOfABI, tokenContract)

Next, call methods.balanceOf() on the contract and pass the tokenHolder address. This call sends a request to your Infura endpoint to request the token balance in the tokenHolder account address.

Create the below async function getTokenBalance that accomplishes this by interacting with the tokenContract.

async function getTokenBalance() {
  const result = await.contract.methods.balanceOf(tokenHolder).call();
  console.log(result)
}

getTokenBalance();

7. Convert the token units​

By default, calling balanceOf returns the balance value in wei, which is the smallest unit in Ethereum, equal to 0.000000000000000001 Ether (10-18).

Use web3.utils.fromWei(result, "ether") to get the actual number of DAI tokens, by adding the following line to the async function:

const formattedResult = web3.utils.fromWei(result, "ether")

Also, update your console.log(format):

console.log(formattedResult)

8. Run the script​

Complete code​

Here is the complete code for retrieveBalance.js. Before running it make sure you replace <YOUR-API-KEY> with your Infura API key.

const { Web3 } = require("web3")
const web3 = new Web3(
  new Web3.providers.HttpProvider("https://mainnet.infura.io/v3/<YOUR-API-KEY>")
)

const balanceOfABI = [
  {
    constant: true,
    inputs: [
      {
        name: "_owner",
        type: "address",
      },
    ],
    name: "balanceOf",
    outputs: [
      {
        name: "balance",
        type: "uint256",
      },
    ],
    payable: false,
    stateMutability: "view",
    type: "function",
  },
]

// DAI token contract
const tokenContract = "0x6B175474E89094C44Da98b954EedeAC495271d0F"
// A DAI token holder
const tokenHolder = "0x075e72a5eDf65F0A5f44699c7654C1a76941Ddc8"
const contract = new web3.eth.Contract(balanceOfABI, tokenContract)

async function getTokenBalance() {
  const result = await contract.methods.balanceOf(tokenHolder).call()
  const formattedResult = web3.utils.fromWei(result, "ether")
  console.log(formattedResult)
}

getTokenBalance()

Run the script using the following command:

node retrieveBalance.js