Here is the article:
Upgrading to Ethereum Web3 v4.7.0: Easily Capturing Broadcast Events
As a developer building complex applications on top of the Ethereum blockchain, one of the most challenging tasks we face is handling events emitted by the network. In our case, we upgraded from version 1.x.x (the legacy version) to version 4.7.0 (our new favorite version), and now we can’t wait to learn how to easily handle these broadcast events.
The first step to using Ethereum Web3 v4.7.0 is to understand the process of event broadcasting. Typically, when an event is broadcast by a contract or its function call, it triggers a callback that is broadcast to all connected nodes in the network. This allows other applications and contracts to react to the event.
To capture these events with our web3.js library (v4.7.0), we can use the “on” method provided by Web3.js. Here is an example of how to do this.
// Importing the required modules
const Web3 = require('web3');
const web3 = new Web3();
// Get an instance of the Ethereum provider
const provider = new web3.providers.HttpProvider('
// Define a function to handle broadcast events
function onEvent(event) {
// Check if this event is interesting (e.g. "New Block")
if (event.type === 'NewBlock') {
console.log(Received new block: ${event.data});
}
}
// Subscribe to broadcast events
web3.eth.on('block', onEvent);
// You can also specify a specific event type and callback function
web3.eth.on('TransactionHash', oneEvent);
In this example, we import the Web3.js library and create an instance of the Ethereum service provider. We then define an “on” method that listens for the broadcast events of interest (in our case, “NewBlock”). The “onEvent” callback function is called whenever an event broadcast over the network is received.
When you are ready to disconnect from the network, simply call the off method on your instance:
web3.eth.off('block', onEvent);
Following this example and using Web3.js v4.7.0, we can easily capture broadcast events in our applications and react accordingly.
Tips and Variations
- Be sure to replace “ with your actual Infura project ID.
- You can also specify a callback function or event handler as an argument to the “on” method, for example: “web3.eth.on(‘NewBlock’, onEvent)”.
- Note that events are only emitted when a contract is called. For example, if you call a contract function from another contract, it will not emit an event.
- If you need more control over the event handling process (e.g. for complex use cases), consider using Web3.js v5.x.x.
We hope this helps! Let us know in the comments if you have any questions or need further assistance.