MetaMask React

Simplistic Context provider and consumer hook in order to manage MetaMask in the browser.

Installation

The recommend way to use MetaMask React with a React app is to install it as a dependency.

If you use npm:

npm install metamask-react

Or if you use yarn:

yarn add metamask-react

Quick Start

The first step is to wrap you App or any React subtree with the MetaMaskProvider

// index.js
import { MetaMaskProvider } from "metamask-react";

...

ReactDOM.render(
  <React.StrictMode>
    <MetaMaskProvider>
      <App />
    </MetaMaskProvider>
  </React.StrictMode>,
  document.getElementById('root')
);

In any React child of the provider, one can use the useMetaMask hook in order to access the state and methods.

// app.js
import { useMetaMask } from "metamask-react";

...

function App() {
    const { status, connect, account, chainId, ethereum } = useMetaMask();

    if (status === "initializing") return <div>Synchronisation with MetaMask ongoing...</div>

    if (status === "unavailable") return <div>MetaMask not available :(</div>

    if (status === "notConnected") return <button onClick={connect}>Connect to MetaMask</button>

    if (status === "connecting") return <div>Connecting...</div>

    if (status === "connected") return <div>Connected account {account} on chain ID {chainId}</div>

    return null;
}

Statuses and behaviour

The MetaMaskProvider will first initialise the state with initializing status, the account and chainId will be null. A synchronization is performed in order to derive the MetaMask state.

If the ethereum object is not present or if it is not the one associated to MetaMask, the synchronisation will change the status to unavailable.

Otherwise, a check is performed in order to detect if MetaMask has already connected accounts for the application.

In case of no connected accounts, the status will be notConnected, otherwise the status will be connected.

Here is an abstract on the different statuses:

• initializing: the provider is currently initializing by synchronizing with MetaMask
• unavailable: MetaMask is not available, nothing will be done
• notConnected: MetaMask is available but not connected to the application
• connected: MetaMask is connected to the application
• connecting: the connection of your accounts to the application is ongoing

Chain utils

The context exposes two methods in order to facilitate the management of the networks. These methods are wrappers around the JSON RPC requests handled by MetaMask, see MetaMask documentation for additonal informations.

The first one is to request a switch to a different network

function WrongNetwork() {
  const { switchChain } = useMetaMask();
  // Request a switch to Ethereum Mainnet
  return (
    <button onClick={() => switchChain("0x1")}>Switch to Ethereum Mainnet</button>
  )
}

The second one is a request to add to MetaMask a network and then connect to it

function WrongNetwork() {
  const { addChain } = useMetaMask();
  const gnosisChainNetworkParams = {
    chainId: "0x64",
    chainName: "Gnosis",
    nativeCurrency: {
        name: "xDai",
        symbol: "XDAI",
        decimals: 18,
    },
    rpcUrls: ["https://rpc.gnosischain.com/"],
    blockExplorerUrls: ["https://gnosisscan.io/"],
  };
  // Request to add Gnosis chain and then switch to it
  return (
    <button onClick={() => addChain(gnosisChainNetworkParams)}>Add Gnosis chain</button>
  )
}

Finally, here is a non exhaustive list of the networks and their chain IDs

const networks = {
  mainnet: "0x1", // 1
  // Test nets
  goerli: "0x5", // 5
  ropsten: "0x3", // 3
  rinkeby: "0x4", // 4
  kovan: "0x2a", // 42
  mumbai: "0x13881", // 80001
  // Layers 2
  arbitrum: "0xa4b1", // 42161
  optimism: "0xa", // 10
  // Side chains
  polygon: "0x89", // 137
  gnosisChain: "0x64", // 100
  // Alt layer 1
  binanceSmartChain: "0x38", // 56
  avalanche: "0xa86a", // 43114
  cronos: "0x19", // 25
  fantom: "0xfa" // 250
}

Type safe hook

Most of the time, the application will use the state when the user is connected, i.e. with status connected. Therefore the hook useConnectedMetaMask is additionally exposed, it is the same hook as useMetaMask but is typed with the connected state, e.g. the account or the chainId are necessarily not null. This hook is only usable when the status is equal to connected, it will throw otherwise.

function MyComponent() {
  const {
    // typed as string - can not be null
    account,
    // typed as string - can not be null
    chainId
  } = useConnectedMetaMask();

  return <div>Connected account {account} on chain ID {chainId}</div>
}

Contributing :rocket:

Contributions are welcome! Please follow the guidelines in the contributing document.