Get ether and erc-20 token balances in a wallet

main.js

const ethers = require('ethers')
const { toChecksumAddress } = require('ethereum-checksum-address')
require('dotenv').config()

const main = async () => {
    // Connect to an EVM network
    const provider = new ethers.providers.JsonRpcProvider(`https://polygon-mainnet.g.alchemy.com/v2/${process.env.RPC_KEY}`)
    // Create a wallet
    const wallet = new ethers.Wallet(process.env.PRIVATE_KEY)
    // Get a signer
    const signer = wallet.connect(provider)
    // Get the Ether balance in wallet
    const balance = await provider.getBalance(wallet.address)
    console.log(balance.toString())

    // Create an erc-20 abi 
    const IERC20 = [
        'function name() external pure returns(string memory)',
        'function symbol() external pure returns(string mamory)',
        'function totalSupply() external view returns(uint256)',
        'function balanceOf(address owner) external view returns (uint256)',
        'function allowance(address owner, address spender) external view returns (uint256)',
        'function approve(address spender, uint256 value) external returns (bool)',
        'function transfer(address to, uint256 value) external returns (bool)',
        'function transferFrom(address from, address to, uint256 value) external returns (bool)'
    ]

    // Checksum the token address
    let address = toChecksumAddress('0x385Eeac5cB85A38A9a07A70c73e0a3271CfB54A7')
    // Make a js obj of a token contract
    const token = new ethers.Contract(address, IERC20, signer)
    // Get the token erc-20 token balance
    let ercBalance = await token.balanceOf(wallet.address)
    console.log(ercBalance.toString())

}

main()
    .then(() => process.exit(0))
    .catch((err) => {
        console.error(err)
        process.exit(1)
    })