web3

What is web3?

The web3 npm package is a collection of libraries that allow you to interact with a local or remote Ethereum node, using HTTP, IPC, or WebSocket. It provides functionalities for interacting with smart contracts, sending transactions, and querying blockchain data.

What are web3's main functionalities?

Connecting to an Ethereum Node

This feature allows you to connect to an Ethereum node using an HTTP provider. You can replace the URL with your own node's URL or use a service like Infura.

const Web3 = require('web3');
const web3 = new Web3('https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID');

Interacting with Smart Contracts

This feature allows you to interact with smart contracts deployed on the Ethereum blockchain. You need the contract's ABI and address to create a contract instance and call its methods.

const contractABI = [/* ABI array */];
const contractAddress = '0xYourContractAddress';
const contract = new web3.eth.Contract(contractABI, contractAddress);
contract.methods.yourMethod().call().then(console.log);

Sending Transactions

This feature allows you to send transactions on the Ethereum network. You need the sender's account address and private key to sign and send the transaction.

const account = '0xYourAccountAddress';
const privateKey = 'your_private_key';
const tx = {
  to: '0xRecipientAddress',
  value: web3.utils.toWei('0.1', 'ether'),
  gas: 2000000
};
web3.eth.accounts.signTransaction(tx, privateKey).then(signed => {
  web3.eth.sendSignedTransaction(signed.rawTransaction)
    .on('receipt', console.log);
});

Querying Blockchain Data

This feature allows you to query data from the blockchain, such as retrieving the latest block information.

web3.eth.getBlock('latest').then(console.log);

Other packages similar to web3

ethers

The ethers.js library aims to be a complete and compact library for interacting with the Ethereum Blockchain and its ecosystem. It provides similar functionalities to web3, such as connecting to Ethereum nodes, interacting with smart contracts, and sending transactions. Ethers.js is known for its smaller size and better documentation.

truffle

Truffle is a development environment, testing framework, and asset pipeline for Ethereum. While it provides some overlapping functionalities with web3, such as interacting with smart contracts, it is more focused on the development and deployment of smart contracts.

embark

Embark is a framework for serverless Decentralized Applications using Ethereum, IPFS, and other platforms. It provides functionalities for smart contract management, decentralized storage, and communication, making it a more comprehensive solution compared to web3.

README

Migration 0.13.0 -> 0.14.0

web3.js version 0.14.0 supports multiple instances of web3 object. To migrate to this version, please follow the guide:

-var web3 = require('web3');
+var Web3 = require('web3');
+var web3 = new Web3();

Ethereum JavaScript API

This is the Ethereum compatible JavaScript API which implements the Generic JSON RPC spec. It's available on npm as a node module, for bower and component as an embeddable js and as a meteor.js package.

You need to run a local Ethereum node to use this library.

Documentation

Installation

Node.js

npm install web3

Yarn

yarn add web3

Meteor.js

meteor add ethereum:web3

As Browser module

Bower

bower install web3

Component

component install ethereum/web3.js

• Include web3.min.js in your html file. (not required for the meteor package)

Usage

Use the web3 object directly from global namespace:

console.log(web3); // {eth: .., shh: ...} // it's here!

Set a provider (HttpProvider)

if (typeof web3 !== 'undefined') {
  web3 = new Web3(web3.currentProvider);
} else {
  // set the provider you want from Web3.providers
  web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
}

Set a provider (HttpProvider using HTTP Basic Authentication)

web3.setProvider(new web3.providers.HttpProvider('http://host.url', 0, BasicAuthUsername, BasicAuthPassword));

There you go, now you can use it:

var coinbase = web3.eth.coinbase;
var balance = web3.eth.getBalance(coinbase);

You can find more examples in example directory.

Contribute!

Requirements

• Node.js
• npm

sudo apt-get update
sudo apt-get install nodejs
sudo apt-get install npm
sudo apt-get install nodejs-legacy

Building (gulp)

npm run-script build

Testing (mocha)

npm test

Community

• Gitter
• Forum

Other implementations

• Python Web3.py
• Haskell hs-web3
• Java web3j
• Scala web3j-scala
• Purescript purescript-web3