Ethereum: Polygon zkEVM error to get token balance: Unable to decode result data

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Ethereum: Polygon zk-EVM Get Token Balance Error

Overview

Ethereum Virtual Machine (EVM) and Zk-SNARKit (zk-Edward Key-Share Proofs) are powerful tools for creating secure and scalable decentralized applications (dApps). However, the integration of these concepts into the Ethereum blockchain can be difficult due to the differences in their architectures. In this article, we will look at why an error occurs when trying to get the balance of each ERC-20 token on the Polygon zk-EVM network using Ethers.js.

Problem

When working with ERC-20 tokens in the Polygon zk-EVM network, an error «failed to extract output data» occurs. This error occurs because the ethers.js library cannot analyze the result of a call to the getBalance() function, which is used to obtain the balance of an ERC-20 token.

Problem

The problem is that the function getBalance() returns a JSON object containing information about the balance. However, Ethers.js expects this object to have a certain format that allows the result to be successfully extracted and parsed. Unfortunately, the ethers.js library cannot process the received JSON data due to its internal implementation.

Solution

This problem can be solved in several ways:

1. Update Ethers.js to version 5.x

The easiest solution is to update Ethers.js to version 5.x or later, which includes improved support for ERC-20 token balances on the zk-EVM network.

npm install ethers@latest

2. Use the ethers.js «getBalance()» function with a custom decode function

The second solution is to create a custom decoding function that can process the JSON data received when the getBalance() function is called.

Here is an example implementation:

const { ethers } = require('ethers');


async function getBalance(tokenAddress) {

  const balance = await ethers.getBalance(tokenAddress);

  return new promise((allow, reject) => {

    ask {

      resolve(balance.data.toString());

    } catch (error) {

      reject (error);

    }

  });

}


getBalance("0x...").then((balance) => {

  console.log(balance); // Print: information about the balance in the form of a line

}).catch((error) => {

  console. error(error);

});

In this example, we define a custom function getBalance() that accepts a character address and returns a promise that converts the balance information to a string. This allows us to successfully process the received JSON data.

Conclusion

By updating Ethers.js to version 5.x or creating a custom decode function, you can resolve the «unable to decode output» error when retrieving the balance of each ERC-20 token on the Polygon zk-EVM network. using Ethers.js.

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