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

npm install web3

Yarn

yarn add web3

In the Browser

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

npm run build

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

Or via jsDelivr CDN:

<script src="https://cdn.jsdelivr.net/npm/web3@latest/dist/web3.min.js"></script>

UNPKG:

<script src="https://unpkg.com/web3@latest/dist/web3.min.js"></script>

Usage

// In Node.js
const Web3 = require('web3');

let 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);

Usage with TypeScript

We support types within the repo itself. Please open an issue here if you find any wrong types.

You can use web3.js as follows:

import Web3 from 'web3';
const web3 = new Web3('ws://localhost:8546');

If you are using the types in a commonjs module, like in a Node app, you just have to enable esModuleInterop and allowSyntheticDefaultImports in your tsconfig for typesystem compatibility:

"compilerOptions": {
    "allowSyntheticDefaultImports": true,
    "esModuleInterop": true,
    ....

Trouble shooting and known issues.

Web3 and Angular

New solution

If you are using Angular version >11 and run into an issue building, the old solution below will not work. This is because polyfills are not included in the newest version of Angular.

• Install the required dependencies within your angular project:

npm install --save-dev crypto-browserify stream-browserify assert stream-http https-browserify os-browserify

• Within tsconfig.json add the following paths in compilerOptions so Webpack can get the correct dependencies

{
    "compilerOptions": {
        "paths" : {
        "crypto": ["./node_modules/crypto-browserify"],
        "stream": ["./node_modules/stream-browserify"],
        "assert": ["./node_modules/assert"],
        "http": ["./node_modules/stream-http"],
        "https": ["./node_modules/https-browserify"],
        "os": ["./node_modules/os-browserify"],
    }
}

• Add the following lines to polyfills.ts file:

import { Buffer } from 'buffer';

(window as any).global = window;
global.Buffer = Buffer;
global.process = {
    env: { DEBUG: undefined },
    version: '',
    nextTick: require('next-tick')
} as any;

Old solution

If you are using Ionic/Angular at a version >5 you may run into a build error in which modules crypto and stream are undefined

a work around for this is to go into your node-modules and at /angular-cli-files/models/webpack-configs/browser.js change the node: false to node: {crypto: true, stream: true} as mentioned here

Another variation of this problem was an issue opned on angular-cli

Documentation

Documentation can be found at ReadTheDocs.

Building

Requirements

• Node.js
• npm

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

Building (webpack)

Build the web3.js package:

npm run build

Testing (mocha)

npm test

Contributing

Please follow the Contribution Guidelines and Review Guidelines.

This project adheres to the Release Guidelines.

Community

• Discord
• StackExchange

Similar libraries in other languages

• Haskell: hs-web3
• Java: web3j
• PHP: web3.php
• Purescript: purescript-web3
• Python: Web3.py
• Ruby: ethereum.rb
• Scala: web3j-scala

Semantic versioning

This project follows semver as closely as possible from version 1.3.0 onwards. Earlier minor version bumps might have included breaking behavior changes.