> For the complete documentation index, see [llms.txt](https://docs.lycanchain.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.lycanchain.com/developers-integration/smart-contracts/interaction/web3.js.md).

# Web3.js

Web3.js is a robust and flexible collection of TypeScript and JavaScript libraries that allows developers to interact with Lycan nodes over HTTP, IPC or WebSocket connections.

Check out web3js for [installation details](https://docs.web3js.org/guides/getting_started/quickstart#installation) and [an overview](https://docs.web3js.org/).

**Initializing Web3.js with Lycan Chain**

Once you have Web3.js installed, you need to set up a Web3 instance and connect it to the Lycan Chain network. Here’s how you can do it:

```javascript
const Web3 = require('web3');

// Connect to the Lycan Chain RPC URL
const web3 = new Web3('https://rpc.lycanchain.com');

// Set default chain parameters
web3.eth.defaultCommon = {
    customChain: {
        name: 'Lycan',
        chainId: 721,
        networkId: 721
    }
};
```

This code initializes Web3.js and connects it to the Lycan Chain using the provided RPC URL. The `defaultCommon` parameter is configured to specify the custom chain details for Lycan Chain.

#### Interacting with Smart Contracts

**Initializing a Contract**

To interact with a smart contract on Lycan Chain, you'll need the contract's ABI (Application Binary Interface) and its deployed address. Here’s an example of how to initialize a contract:

```javascript
// ABI of the smart contract
const contractABI = [
    // ABI details here
];

// Address of the deployed contract
const contractAddress = '0xYourContractAddressHere';

// Create a contract instance
const myContract = new web3.eth.Contract(contractABI, contractAddress);
```

#### Advanced Configuration

**Custom Chain Configuration**

By setting `web3.eth.defaultCommon`, you ensure that Web3.js is aware of the custom chain parameters for Lycan Chain. This is crucial for correctly signing transactions and interacting with the network.

```javascript
web3.eth.defaultCommon = {
    customChain: {
        name: 'Lycan',
        chainId: 721,
        networkId: 721
    }
};
```

This configuration tells Web3.js to use the specified chain ID and network ID for all interactions, ensuring compatibility with Lycan Chain.