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web3.js

web3.js is a JavaScript library that allows developers to interact with EVM-compatible blockchain networks. You can use web3.js to interact with smart contracts deployed on the Base network.

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Install

To install web3.js run the following command: 
npm install web3

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Setup

Before you can start using web3.js, you need to import it into your project. Add the following line of code to the top of your file to import web3.js: 
//web3.js v1
const Web3 = require('web3');

//web3.js v4
const { Web3 } = require('web3');

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Connecting to Base

You can connect to Base by instantiating a new web3.js Web3 object with a RPC URL of the Base network: 
const { Web3 } = require('web3');

const web3 = new Web3('https://mainnet.base.org');
To alternatively connect to Base Sepolia (testnet), change the above URL from https://mainnet.base.org to https://sepolia.base.org.

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Accessing data

Once you have created a provider, you can use it to read data from the Base network. For example, you can use the getBlockNumber method to get the latest block: 
async function getLatestBlock(address) {
  const latestBlock = await web3.eth.getBlockNumber();
  console.log(latestBlock.toString());
}

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Deploying contracts

Before you can deploy a contract to the Base network using web3.js, you must first create an account. You can create an account by using web3.eth.accounts: 
const privateKey = "PRIVATE_KEY";
const account = web3.eth.accounts.privateKeyToAccount(privateKey);
PRIVATE_KEY is the private key of the wallet to use when creating the account.

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Interacting with smart contracts

You can use web3.js to interact with a smart contract on Base by instantiating a Contract object using the ABI and address of a deployed contract: 
const abi = [
... // ABI of deployed contract
];

const contractAddress = "CONTRACT_ADDRESS"

const contract = new web3.eth.Contract(abi, contractAddress);
Once you have created a Contract object, you can use it to call desired methods on the smart contract: 
async function setValue(value) {
  // write query
  const tx = await contract.methods.set(value).send();
  console.log(tx.transactionHash);
}

async function getValue() {
  // read query
  const value = await contract.methods.get().call();
  console.log(value.toString());
}
For more information on deploying contracts on Base, see Deploying a Smart Contract.