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

PREVIEW RELEASE This is a beta preview release with breaking changes! The current stable version is 0.20.0

web3.js - Ethereum JavaScript API

This is the Ethereum JavaScript API which connects to the Generic JSON RPC spec.

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

Please read the documentation for more.

Installation

Node.js

npm install web3

Meteor.js

Note: works only in the Browser for now. (PRs welcome)

meteor add ethereum:web3

In the Browser

Use the prebuild dist/web3.min.js, or build using the web3.js repository:

npm run-script build

Then include dist/web3.js in your html file. This will expose the Web3 object on the window object.

Usage

// in node.js
var Web3 = require('web3');

var web3 = new Web3('ws://localhost:8546');
console.log(web3);
> {
    eth: ... ,
    shh: ... ,
    utils: ...,
    ...
}

Additionally you can set a provider using web3.setProvider() (e.g. WebsocketProvider)

web3.setProvider('ws://localhost:8546');
// or
web3.setProvider(new Web3.providers.WebsocketProvider('ws://localhost:8546'));

There you go, now you can use it:

web3.eth.getAccounts()
.then(console.log);

Documentation

Documentation can be found at read the docs

Building

Requirements

• Node.js
• npm

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

Building (gulp)

Build only the web3.js package

npm run-script build

Or build all sub packages as well

npm run-script build-all

This will put all the browser build files into the dist folder.

Testing (mocha)

npm test