README.md

@substrate/connect

An NPM package that offers an innovative way to interact with Substrate-based blockchains directly in your browser.

The primary implementation of the light-client provider for any Substrate-based chain.

Using @substrate/connect for library authors

The connect package searches for a light client provider via the discovery protocol. If none is found, it will initiate a smoldot instance in the user's browser tab.

Example Usage

To connect to a well-known chain ('polkadot', 'ksmcc3', 'westend2', 'rococo_v2_2'):

import { createScClient, WellKnownChain } from "@substrate/connect"

const scClient = createScClient()
const chain = await scClient.addWellKnownChain(
  WellKnownChain.westend2,
  function jsonRpcCallback(response) {
    console.log("response", response)
  },
)

chain.sendJsonRpc(
  '{"jsonrpc":"2.0","id":"1","method":"system_health","params":[]}',
)

To connect to a custom Substrate chain using its name and chainspec:

import { createScClient } from "@substrate/connect"
import myJsonChainSpec from "./mySubstrateChainSpec.json"

const myChainSpec = JSON.stringify(myJsonChainSpec)

const scClient = createScClient()
const chain = await scClient.addChain(
  myChainSpec,
  function jsonRpcCallback(response) {
    console.log("response", response)
  },
)

chain.sendJsonRpc(
  '{"jsonrpc":"2.0","id":"1","method":"system_health","params":[]}',
)

Connecting to a Parachain

To connect to a parachain, first instantiate the relay chain it is connected to, then instantiate the parachain on the same relay chain. The following example connects to a parachain on the Westend test network:

import { createScClient, WellKnownChain } from "@substrate/connect"
import jsonParachainSpec from "./myParaChainSpec.json"

const parachainSpec = JSON.stringify(jsonParachainSpec)

const scClient = createScClient()
const relayChain = await scClient.addWellKnownChain(WellKnownChain.westend2)
const parachain = await relayChain.addChain(
  parachainSpec,
  function jsonRpcCallback(response) {
    console.log("response", response)
  },
)

parachain.sendJsonRpc(
  '{"jsonrpc":"2.0","id":"1","method":"system_health","params":[]}',
)

PolkadotJs Example

yarn add @polkadot/rpc-provider
yarn add @polkadot/api

import { ScProvider } from "@polkadot/rpc-provider/substrate-connect"
import * as Sc from "@substrate/connect"
import { ApiPromise } from "@polkadot/api"

// Connect to polkadot relay chain
const provider = new ScProvider(Sc, Sc.WellKnownChain.polkadot)
await provider.connect()
const api = await ApiPromise.create({ provider })

// Connect to parachain
const provider2 = new ScProvider(Sc, Sc.WellKnownChain.people, provider)
await provider2.connect()
const api2 = await ApiPromise.create({ provider })

Scripts

• pnpm test to run the unit tests
• pnpm build to build @substrate-connect
• pnpm lint to run linter for @substrate-connect