Ethereum: Polygon zkEVM get token balance Error: could not decode result data
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Ethereum: Polygon zk-EVM Get Token Balance Error
Overview
The Ethereum Virtual Machine (EVM) and Zk-SNARKs (zk-Edward Key-Share Proofs) are powerful tools for building secure and scalable decentralized applications (dApps). However, integrating these concepts into the Ethereum blockchain can be challenging due to their different architectures. In this article, we explore why an error occurs when attempting to get the balance of each ERC-20 token on the Polygon zk-EVM network using Ethers.js.
The Problem
When working with ERC-20 tokens on the Polygon zk-EVM network, you encounter the “Failed to decode result data” error. This error occurs because the ethers.js library cannot parse the result of the getBalance() function call used to retrieve the balance of an ERC-20 token.
The Problem
The problem arises because the getBalance() function returns a JSON object with the balance data. However, Ethers.js expects this object to be in a specific format where it can successfully decode and parse the result. Unfortunately, the ethers.js library cannot handle the resulting JSON data due to its internal implementation.
Solution
To fix this problem, you have a few options:
1. Update Ethers.js to version 5.x
The simplest solution is to update Ethers.js to version 5.x or higher, 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
Another solution is to create a custom decode function that can process the resulting JSON data from the getBalance() function call.
Here is a sample implementation:
const { ethers } = require('ethers');
async function getBalance(tokenAddress) {
const balance = await ethers.getBalance(tokenAddress);
return new Promise((resolve, reject) => {
try {
resolve(balance.data.toString());
} catch (error) {
reject(error);
}
});
}
getBalance("0x...").then((balance) => {
console.log(balance); // Output: the balance data as a string
}).catch((error) => {
console.error(error);
});
In this example, we define a custom function getBalance() that takes a token address and returns a promise that resolves the balance data as a string. This allows us to successfully process the resulting JSON data.
Conclusion
By updating Ethers.js to version 5.x or creating a custom decoding function, you should be able to resolve the “Failed to decode result data” error when retrieving the balance of each ERC-20 token on the Polygon zk-EVM network using Ethers.js.