Displaying custom Solidity errors on the front-end

When building complex decentralized applications (dApps), it is common to encounter custom errors that cannot be detected by traditional error handling mechanisms. In this article, we will explore how to display these custom errors on the front-end using Ethereum’s web3.js library.

Why are custom errors displayed?

Custom errors are often the result of unexpected logic in your contract or third-party integrations. By displaying them on the front-end, you can:

  • Improve user experience

    : Users will appreciate a clear indication that something went wrong.

  • Improve debugging tools: Developers can use these custom errors to identify and debug issues more effectively.

Prerequisites

Before we get started, make sure you have:

  • Basic knowledge of Solidity and web3.js
  • A contract implemented on the Ethereum blockchain

Displaying custom errors with web3.js

In this example, we’ll use web3.js to display custom errors in a frontend application. We’ll create an event emitter that listens for CustomError events emitted by your contract.

First, install the web3.js and w3-logger libraries:

npm install web3 w3-logger

Contract execution

pragma-solidity 0.8.16;
test-contract {
event CustomError(uint256 value);
public-opinion;
public constructor() {
emit CustomError(10); // Example error code
}
function testFunction() returns pure extern (bool) {
a = 5; // This should throw a custom error
returns true; // Successful execution
}
}

Frontend implementation

import * as w3 from "web3";
import { Events } from "w3-logger";
class FrontendApp {
constructor(w3Instance) {
this.w3 = w3Instance;
const eventEmitter = new Events();
eventEmitter.on("CustomError", (error value) => {
console.error(Custom error: ${errorValue});
// Handle custom error logic here
});
// Implement contract
deployContract(w3Instance);
}
async deployContract(w3Instance) {
const contractAddress = "0x …"; // Replace it with your contract address.
const contractAbi = "..."; // Replace it with your ABI contract
const web3 = new w3.Web3(w3Instance, contractAbi);
await web3.eth.deployContract(contractAddress);
}
}

Running the frontend

To run this frontend application, you need to create and deploy a new Solidity contract. Next, import the FrontendApp class and call its constructor.

const w3Instance = require("web3")("
const frontendApp = new FrontendApp(w3Instance);

Custom Error Handling

In your application front-end: You can handle custom errors using a try-catch block:

try {
const result = await frontendApp.testFunction();
console.log(result);
} catcherror {
console.error(Custom error: ${error.message});
}

Displaying custom errors on the front-end can improve the user experience of your application, and can make it easier for developers to identify and fix problems.

Conclusion

Displaying custom errors is an essential step in building robust decentralized applications. By using “web3.js” and implementing a custom error handling system, you can improve the usability and debugging capabilities of your application. front-end. This example shows how to implement a contract on the Ethereum blockchain and display custom errors on the front-end using web3.js.

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