Onboard (older version)

This page is for Onboard v1, which is an older version. For web3-onboard which is the newest, modernized version, see the web3-onboard page.
Use the latest version of Onboard at https://github.com/blocknative/web3-onboard . This version is no longer maintained.
See our Migration guide here to migrate to web3-onboard from the older version
Example desktop wallet select modal
Example mobile wallet select modal
Quickstart
It should take less than 5 minutes to get going with Blocknative Onboard.
Create a Blocknative Account
Go to the Account Dashboard at https://explorer.blocknative.com/account and setup an account with an email address. You will receive an email to confirm your account.
Create your API Key
On the Account Dashboard at https://explorer.blocknative.com/account, create an API key with your choice of name or use/rename the Default Key. Consider using different API keys for development, staging, and production releases.
Install the widget using npm
npm install bnc-onboard
Initialize the Library
Use the minimum required config. There are more options available as detailed in the initialization section.
import Onboard from 'bnc-onboard'
import Web3 from 'web3'
​
let web3;
​
const onboard = Onboard({
  dappId: apiKey,       // [String] The API key created by step one above
  networkId: networkId,  // [Integer] The Ethereum network ID your Dapp uses.
  subscriptions: {
    wallet: wallet => {
       web3 = new Web3(wallet.provider)
    }
  }
});
​
The wallet subscription function will be called when the user selects a wallet so you can instantiate web3 with the selected provider.
Onboard User
Ask the user to select a wallet and then check wallet is ready to transact.
await onboard.walletSelect();
await onboard.walletCheck();
And you are live!
Screencasts
See the above Quickstart guide in a screencast:
Onboard.js Quickstart Screencast
For a deeper dive with additional wallets that builds on the Quick Start, see this screencast:
Additional Wallets Screencast
Example Code
For an example of a basic React demo integration of both Onboard.js and Notify.js, checkout the GitHub repo:

https://github.com/blocknative/onboard-notify-react​
and the live demo:
​https://reactdemo.blocknative.com/ ​
Initialization
Options
const options = {
  dappId: String,
  networkId: Number,
  networkName: String,
  darkMode: Boolean,
  blockPollingInterval: Number,
  subscriptions: {
    address: Function, 
    network: Function,
    balance: Function,
    wallet: Function
  },
  walletSelect: {
    heading: String,
    description: String,
    explanation: String,
    wallets: Array,
    agreement: {
      version: String,
      termsUrl: String,
      privacyUrl: String
    }
  },
  walletCheck: Array
}
dappId - [optional]
Your unique apiKey that identifies your application. You can generate a dappId by visiting the Blocknative account page and create a free account. The dappid enables Onboard to use Blocknative notification services to efficiently maintain address balance state. This is not required to use Onboard to connect wallets to Dapps. It is required to efficiently get an up to date wallet balance value via the balance subscription or getState() calls.
Efficiently getting an up to date wallet balance value is subject to our API Rate Limits.
networkId - [required]
The Ethereum network id that your application runs on. The following values are valid:
1 main Ethereum Network mainnet
3 ropsten Ethereum Network testnet
4 rinkeby Ethereum Network testnet
5 goerli Ethereum Network testnet
28 boba-rinkeby Boba Network Rinkeby testnet
42 kovan Ethereum Network testnet
56 bsc Binance Smart Chain Network mainnet
100 xdai xDai POA Network mainnet
137 polygon Polygon-Matic Network mainnet
250 fantom-opera Fantom Network mainnet
288 boba Boba Network mainnet
4000 fantom-testnet Fantom Network testnet
networkName - [optional] 
This option allows one to specify a custom network name for all non-supported networks (see networkId above for supported networks). For instance, if you set networkId: 56 for Binance smart chain and the user is connected to a different network, the wallet select modal will show local as the network to switch to. But if you specify networkName: "Binance Mainnet" then this will display instead of local.
darkMode - [optional] - Default: false
Opt for the Dark color scheme or not.
blockPollingInterval - [optional] - Default: 4000
Change the rate at which blocks are polled by provider, default is set to 4 seconds.
hideBranding - [optional]
If no dappId is provided, then "Powered by Blocknative" branding will be displayed on all modals. You can choose to hide the branding by setting hideBranding: true. If you have included a dappId then the branding will be hidden by default. If you would like the branding to display when including a dappId then set hideBranding: false.
subscriptions - [optional]
An object of callback functions that get called whenever the corresponding value changes. Use these callbacks to sync your UI or to store the values for use elsewhere in your code. Valid parameters to register callbacks for are: 
address - called with the user's current address [string]
ens - called with the user's current ens name (if available) [object]
name  - The user's resolved ens name [string]
avatar - A link to the user's avatar [string]
getText - A function to retrieve the user's text records [function]
contentHash - The user's content hash record [string]
network - called with the user's current network id [number]
balance - called with the user's current balance [string]
wallet - called with the user's current wallet [object]
provider - The JavaScript provider for interacting with the wallet
name - The wallet display name
instance - If the wallet type is 'sdk' then this is the initialized wallet instance
type - The wallet type 'hardware' | 'injected' | 'sdk'
connect - The function that initiates the wallet connection logic
dashboard - Some SDK wallets allow for opening to wallet dashboard
icons - [object] Image strings for the wallet icon { svg, src, srcset }
 walletSelect - [optional]
A object that defines how the wallet select screen will render using the following parameters:
heading - [optional] : A string that will be the wallet select modal heading
description - [optional] : A string that will be the wallet select modal description
explanation - [optional] : A string that will be included in the "What is a Wallet" section 
wallets - [optional] : An array of wallet modules or wallet initialization objects that the user can select from
agreement - [optional]: An object containing properties for use with terms of service agreement
version - The current version of the terms that the user needs to agree to. When this value is updated the user's agreement is invalidated and they must re-agree upon next usage.
termsUrl - [optional]: A string that will be used for the terms of service url that a user can agree to before using onboard
privacyUrl - [optional]: A string that will be used for the privacy policy url that a user can agree to before using onboard
If not provided, then the default heading and description and wallets that don't require initialization will be included for you.
walletCheck - [optional]
An array of wallet check modules or wallet check initialization objects that will be used to check if the user is ready to transact.
Initialize Onboard
To initialize Onboard, simply import the library and call it with your initializationOptions:
import Onboard from 'bnc-onboard'
​
const initializationOptions = {
    // ..... options here
}
​
const onboard = Onboard(initializationOptions)
The return value will be the initialized onboard library which contains the API functions below.
Customizing 'unknown' Network Name 
If you initialize Onboard with a networkId that is not one of the supported networks all modals will refer to that network with the name unknown. You can name unrecognized networks by also passing in a networkName in to your initialization object:
const onboard = Onboard({
  // ... other init options
  networkId: 137,
  networkName: 'matic'
})
Local Networks
If you are using a local network for testing, you can ensure that the onboarding checks work correctly by setting the networkId for that local network to a number that is not taken by other valid networks.
If you are using the ganache-cli for instance, you can set the networkId via the -i flag:
ganache-cli -i 35
This will set the Ganache networkId to 35
Then in your Onboard config, also set the networkId property to the same value:
const onboard = Onboard({
  networkId: 35,
  // ...other config options
})
API
walletSelect
When you are ready to get a user to select a wallet and connect it to your Dapp, you can call the walletSelect function to display the wallet select modal:
const walletSelected = await onboard.walletSelect()
// returns a Promise that:
// resolves with true if the user selected a wallet
// resolves with false if the user exited from the wallet select modal
This function will show a modal that displays buttons for all of the wallets that you initialized onboard with. It will guide the user through the process of connecting to the wallet that they select. Once the process is successful the function will resolve with true. This means that the provider subscription will have been called with the provider of the selected wallet and you can go ahead and instantiate your web3 library with the provider and also instantiate your contracts.
The walletSelect function can also be called with a autoSelectWallet string. If the string passed in is a valid walletName, then Onboard will automatically select that wallet for the user. This enables saving the previously selected wallet in localStorage and automatically selecting it for the user when they next visit your Dapp.
walletCheck
Once a wallet is selected, you will want to make sure that the user's wallet is prepared and ready to transact by calling the walletCheck function:
const readyToTransact = await onboard.walletCheck()
// returns a Promise that:
// resolves with true if user is ready to transact
// resolves with false if user exited before completing all wallet checks
This function will run through the walletCheck modules that were passed in via initialization sequentially, making sure the user has passed the condition contained in each module and eventually resolves with true if the user completed the sequence. This means that the user is ready to transact. This function is useful to call before every transaction to make sure that nothing has changed since the last time it was called.
walletReset
You may want to reset all of Onboard's internal wallet state and also disconnect from any active SDK instances when a user logs out of your app. You can call the walletReset function to do this easily.
// user wants to log out of session and the wallet state needs to be reset...
onboard.walletReset()
// this method is synchronous and returns undefined
accountSelect
If you want to show the account select modal for hardware wallets at any time you can call the accountSelect function. For example you could display a button that allows the user switch accounts:
<button onclick="onboard.accountSelect()">Switch Account</button>
getState
This function will give you the current state of the user:
const currentState = onboard.getState()
console.log(currentState)
// {
//    address: string
//    network: number
//    balance: string
//    wallet: Wallet
//    mobileDevice: boolean
//    appNetworkId: number
// }
config
You can update some configuration parameters by passing a config object in to the config function:
onboard.config({ darkMode: true, networkId: 4 })
Available parameters that you can update are:
darkMode - [boolean]
networkId - [number]
Built-in Modules
Wallet Modules
Initialization:
To initialize the built in wallet modules, an array of wallet initialization objects needs to be passed to the walletSelect.wallets parameter of the Onboard initialization object. The order of the array is the order that the wallets will be displayed. Mobile wallets will be displayed when a user is on a mobile device and desktop wallets are displayed when they are on a desktop device. 
Each wallet initialization object has additional optional customization parameters:
preferred - Boolean
 Will define whether it is shown at the top of the selection screen. If any of the wallets are set to preferred, then all other wallets that aren't, will be hidden until the user clicks the "Show More" button. If there are no wallets set to preferred, then the first four wallets will be shown and the remaining wallets will be hidden until the show more button is clicked.
label - String
Will over ride the wallet name that is displayed on the button.
svg - String
An svg string that will over ride the icon that is displayed on the button.
iconSrc - String 
An alternative to providing the svg string, by providing a url source.
display - Object 
Customize which wallets to display based on which device a user is using. Note: For wallets that are mobile or desktop only this option will not override this. For instance, if a wallet is mobile only setting display: { desktop: true } will not display this wallet on desktop.
desktop - Boolean default: true
mobile - Boolean default: true
An example configuration that includes all of the supported wallets:
import Onboard from 'bnc-onboard'
​
const FORTMATIC_KEY = "Your Fortmatic key here"
const PORTIS_KEY = "Your Portis key here"
const INFURA_KEY = "Your Infura key here"
const APP_URL = "Your app url here"
const CONTACT_EMAIL = "Your contact email here"
const RPC_URL = "https://<network>.infura.io/v3/<INFURA_KEY>"
const APP_NAME = "Your app name here"
​
const wallets = [
  { walletName: "coinbase", preferred: true },
  { walletName: "trust", preferred: true, rpcUrl: RPC_URL },
  { walletName: "metamask", preferred: true },
  { walletName: "authereum" },
  {
    walletName: 'trezor',
    appUrl: APP_URL,
    email: CONTACT_EMAIL,
    rpcUrl: RPC_URL
  },
  {
    walletName: 'ledger',
    rpcUrl: RPC_URL
  },
  {
    walletName: 'lattice',
    rpcUrl: RPC_URL,
    appName: APP_NAME
  },
  {
    walletName: 'keepkey',
    rpcUrl: RPC_URL
  },
  {
    walletName: 'mewwallet',
    rpcUrl: RPC_URL
  },
  { 
    walletName: 'cobovault',
    rpcUrl: RPC_URL,
    appName: APP_NAME,
  },
  { 
    walletName: 'keystone',
    rpcUrl: RPC_URL,
    appName: APP_NAME,
  },
  {
    walletName: "fortmatic",
    apiKey: FORTMATIC_KEY,
    preferred: true
  },
  {
    walletName: "portis",
    apiKey: PORTIS_KEY,
    preferred: true,
    label: 'Login with Email'
  },
  {
    walletName: "walletConnect",
    infuraKey: INFURA_KEY
  },
  { walletName: "opera" },
  { walletName: "operaTouch" },
  { walletName: "torus" },
  { walletName: "status" },
  { walletName: "walletLink" rpcUrl: RPC_URL, appName: APP_NAME }
  { walletName: "imToken", rpcUrl: RPC_URL },
  { walletName: "meetone" },
  { walletName: "mykey", rpcUrl: RPC_URL },
  { walletName: "huobiwallet", rpcUrl: RPC_URL },
  { walletName: "hyperpay" },
  { walletName: "wallet.io", rpcUrl: RPC_URL },
  { walletName: "atoken" },
  { walletName: "frame" },
  { walletName: "ownbit" },
  { walletName: "alphawallet" },
  { walletName: "gnosis" },
  { walletName: "xdefi" },
  { walletName: "bitpie" },
  { walletName: "binance" },
  { walletName: "liquality" },
  { walletName: "tally" },
  { walletName: "blankwallet" },
  { walletName: "mathwallet" },
  { walletName: "1inch" },
  { walletName: "ronin" },
]
​
const onboard = Onboard({
  //... other options
  walletSelect: {
     wallets: wallets 
  }
})
The following list of  wallet modules are included in Onboard and their initializationObject is listed for each wallet:
Wallets
detectedwallet
The detected wallet will be displayed as an option when an injected Ethereum provider is detected, but it is not recognized by Onboard. This allows users to connect to your app with any provider that conforms to the EIP-1193 standard.
metamask - (desktop & mobile support)
{ walletName: 'metamask' }
authereum  - (desktop & mobile support)
{ 
  walletName: 'authereum',
  disableNotifications: false // [OPTIONAL]
  rpcUri: '<CUSTOM_RPC_URI>' // [OPTIONAL]
  webUri: '<CUSTOM_WEB_URI>' // [OPTIONAL]
  xsUri: '<CUSTOM_XS_URI>' // [OPTIONAL]
  blockedPopupRedirect: true // [OPTIONAL]
}
walletConnect - (desktop & mobile support)
{
  walletName: 'walletConnect',
  infuraKey: 'INFURA_KEY', // your infura id [String][Optional if rpc is provided instead]
  rpc: {
    ['networkId']: '<RPC_ENDPOINT_URL_STRING>'
  }, // [Optional]
  bridge: '<BRIDGE_URL>' // url to a bridge server [String][Optional]
}
portis - (desktop & mobile support)
{
  walletName: 'portis',
  apiKey: 'PORTIS_KEY' // your Portis apiKey [String]
}
fortmatic - (desktop & mobile support) 
{
  walletName: 'fortmatic',
  apiKey: 'FORTMATIC_KEY' // your Fortmatic apiKey [String]
  rpcUrl: '<RPC_ENDPOINT>' // optional - use only for custom networks such as matic
}
trust - (mobile only support)
{ walletName: 'trust' }
coinbase - (mobile only support)
Desktop support for Coinbase Wallet can be found through walletLink module
{ walletName: 'coinbase' }
opera - (desktop & mobile support)
{ walletName: 'opera' }
opera touch - (mobile only support)
{ walletName: 'operaTouch' }
status - (mobile only support)
{ walletName: 'status' }
torus - (desktop & mobile support)
For additional details on the Torus options, check out their docs​
{
  walletName: 'torus',
  rpcUrl: String, // [optional]
  buttonPosition: String, // [optional]
  modalZIndex: Number, // [optional]
  apiKey: String, // [optional]
  buildEnv: String, // 'production' | 'development' | 'staging' | 'testing' | 'lrc' [optional]
  enableLogging: Boolean, // [optional]
  enabledVerifiers: VerifierStatus, // [optional]
  loginConfig: LoginConfig, // [optional]
  showTorusButton: Boolean, // [optional]
  integrity: IntegrityParams, // [optional]
  whiteLabel: WhiteLabelParams, // [optional]
  loginMethod: String // 'google' | 'facebook' | 'twitch' | 'reddit' | 'discord' |  [optional]
}
trezor - (desktop & mobile support)
Trezor requires extra details such as appUrl and email for their manifest​
{
  walletName: 'trezor',
  appUrl: APP_URL, // the url of your app (required for manifest)
  email: CONTACT_EMAIL, // your contact email, (required for manifest)
  rpcUrl: RPC_URL, // url to connect to an RPC endpoint (ie infura)
  // See section Hardware Wallet Custom Networks for more info
  customNetwork: HardwareWalletCustomNetwork
}
ledger - (desktop & mobile support)
Ledger has an additional optional LedgerTransport parameter for when you are building an Electron app and need to pass in the node ledger transport module. You can also use this option to pass in whichever Ledger transport that you would like to use based on feature detection (eg. Windows 10 user might need WebUSB transport instead of the default U2F transport).
{
  walletName: 'ledger',
  rpcUrl: RPC_URL // url to connect to an RPC endpoint (ie infura)
  LedgerTransport: TransportNodeHid,
  // See section Hardware Wallet Custom Networks for more info
  customNetwork: HardwareWalletCustomNetwork
}
lattice - (desktop & mobile support)
{
  walletName: 'lattice',
  rpcUrl: RPC_URL, // url to connect to an RPC endpoint (ie infura)
  appName: APP_NAME // app name that is displayed on device
}
keepkey - (desktop only support)
{
  walletName: 'keepkey',
  rpcUrl: RPC_URL, // url to connect to an RPC endpoint (ie infura)
}
cobovault - (desktop & mobile support)
{
  walletName: 'cobovault',
  rpcUrl: RPC_URL, // url to connect to an RPC endpoint (ie infura)
  appName: APP_NAME // app name that is displayed on device
}
keystone - (desktop & mobile support)
{
  walletName: 'keystone',
  rpcUrl: RPC_URL, // url to connect to an RPC endpoint (ie infura)
  appName: APP_NAME // app name that is displayed on device
}
walletLink - Coinbase Wallet for desktop (desktop only support)
{ 
  walletName: 'walletLink',
  rpcUrl: RPC_URL, // url to connect to an RPC endpoint (ie infura)
  appName: <YOUR_APP_NAME>, // string to label your app 
  appLogoUrl: <YOUR LOGO URL> // string url of your app logo [OPTIONAL]
}
imToken - (mobile only support)
{
  walletName: 'imToken',
  rpcUrl: RPC_URL // url to connect to an RPC endpoint (ie infura)[OPTIONAL]
}
meetone - (mobile only support) 
{ walletName: 'meetone' }
mykey - (mobile only support)
{
  walletName: 'mykey',
  rpcUrl: RPC_URL // url to connect to an RPC endpoint (ie infura)[OPTIONAL]
}
huobiwallet - (mobile only support)
{
  walletName: 'huobiwallet',
  rpcUrl: RPC_URL // url to connect to an RPC endpoint (ie infura)[OPTIONAL]
}
hyperpay - (mobile only support)
{ walletName: 'hyperpay' }
wallet.io - (mobile only support)
{ walletName: "wallet.io", rpcUrl: RPC_URL } // url to connect to an RPC endpoint (ie infura)[OPTIONAL]
atoken - (mobile only support)
{ walletName: "atoken" }
frame - (mobile only support) 
{ walletName: "frame" }
ownbit - (mobile only support)
{ walletName: "ownbit" }
alphawallet - (mobile only support)
{ walletName: "alphawallet" }
gnosis - (desktop only support) 
Gnosis wallet is unique as it designed to be used within the Gnosis Safe Apps interface. If the user opens your dApp within the Safe Apps interface, Gnosis wallet will be automatically selected and the select wallet modal will not be shown. This is to ensure that the user doesn't mistakenly use their wallet instead of their Safe Multisig wallet for the transaction.
{ walletName: "gnosis" }
xdefi - (desktop & mobile support)
{ walletName: "xdefi" }
bitpie - (mobile only support)
{ walletName: "bitpie" }
liquality - (desktop only support)
{ walletName: "liquality" }
binance - (desktop only support)
{ walletName: 'binance' }
mewwallet - (mobile only support)
{
  walletName: 'mewwallet',
  rpcUrl: RPC_URL, // url to connect to an RPC endpoint (ie infura)
}
tally - (desktop only support)
{ walletName: 'tally' }
blankwallet - (desktop only support)
{ walletName: 'blankwallet' }
mathwallet - (desktop & mobile support)
{ walletName: 'mathwallet' }
1inch - (mobile only support)
{ walletName: '1inch' }
Did - (mobile only support)
{ walletName: 'did' }
ronin - (desktop only support)
Ronin now only works on Axie's domains and will open to be used by other domains when the Ronin chain is ready - Updates From Ronin Dev​
Due to the Ronin extension restriction, please add 127.0.0.1 dev.skymavis.one in your hosts file /etc/hosts and access dev.skymavis.one:<port> instead of localhost:<port>.
{ walletName: 'ronin' }
Hardware Wallet Custom Networks
Onboard now supports passing in custom network info for hardware wallets allowing users to use their hardware wallets with non-Ethereum networks such as Energy Web Chain. The customNetwork object is passed to the Common constructor of the @ethereumjs/common library. This is then used to build the transaction that will be signed. Please refer to these instructions for more information. 
Note: Currently only Trezor and Ledger support this functionality/
Example
const onboard = Onboard({
   networkId: 1234
  //... other options
  walletSelect: {
     wallets:[
         {
             walletName: 'ledger',
             rpcUrl: RPC_URL,
             customNetwork: {
                  networkId: number
                  genesis: GenesisBlock
                  hardforks: Hardfork[]
                  bootstrapNodes: BootstrapNode[]
            }
         },
     ] 
  }
})
You can view an example configuration here.
​
​
Wallet Check Modules
Initialization:
To initialize the built in wallet check modules, an array of wallet check initialization objects needs to be passed to the walletCheck parameter of the Onboard initialization object. The order of the array is the order that the checks will be performed. 
Each wallet check initialization object has additional optional customization parameters:
heading - String
Will over ride the heading displayed in the wallet check modal.
description - String
Will over ride the description displayed in the wallet check modal.
icon - String
An svg string that will over ride the icon displayed in the wallet check modal.
button -  { text: String, onclick: () => void} 
An object that defines an extra button's text and onclick function.
html - String
A html string that will be rendered in the modal as html markup underneath the description.
import Onboard from 'bnc-onboard'
​
const walletChecks = [
  { checkName: 'derivationPath' },
  { checkName: 'accounts' },
  { checkName: 'connect' },
  { checkName: 'network' },
  { checkName: 'balance', minimumBalance: '1000000' }
]
​
const onboard = Onboard({
  //... other options
  walletCheck: walletChecks
})
The following wallet check modules are included in Onboard:
connect: Checks that the Dapp has access to the users' accounts and fires the connect function if the selected wallet has one to prompt the user to allow access.
{ checkName: 'connect' }
derivationPath: Provides a UI to allow a user to select or input the derivation path they would like to use with their hardware wallet. Note: will only display if the connected wallet is of type "hardware".
Note: html and button customization parameters won't work for this module as it needs them itself for correct operation.
{ checkName: 'derivationPath' }
accounts: Provides a UI to allow a user to select and load accounts on their hardware wallet. Note: will only display if the connected wallet is of type "hardware".
Note: html and button customization parameters won't work for this module as it needs them itself for correct operation.
{ checkName: 'accounts' }
network: Checks that the users' wallet is connected to the network that the modules were initialized with.
{ checkName: 'network' }
balance: Checks that the users' account has the minimum balance as defined when initialized.
{
  checkName: 'balance',
  minimumBalance: '1000000' // The minimum balance in wei required [String]
}
In order for Onboard to efficiently detect wallet balance changes, a dappId is required when initializing Onboard. This feature is subject to our API Rate Limits.
Creating Custom Modules
Onboard has been built so that custom wallet and wallet check modules can be plugged in to allow for the breadth of different wallets and on-boarding flows that are needed across the web3 ecosystem.
Custom Wallet Modules
A wallet module is an abstraction that allows interoperability between wallets within Onboard.
A wallet module has the following properties:
name - [string][required]
The name of the wallet.
wallet - [function][required]
A function that is called when this wallet is selected. It is called with a helpers object that includes some helper functions that make it easier to create the return object. The helpers object contains the following methods:
getProviderName - A function that takes a provider as an argument and will return the name of the most common providers.
createLegacyProviderInterface - A function that takes the provider as an argument and returns a walletInterface. Legacy refers to a provider that has not implemented EIP-1102.
createModernProviderInterface - A function that takes the provider as an argument and returns a walletInterface. Modern refers to a provider that has implemented EIP-1102. This will work for most providers and is a quick way to create an interface.
BigNumber - A bignumber.js function for number calculations.
getNetwork - A function that takes a provider and will make a JSON-RPC call to get the network.
getAddress - A function that takes a provider and will make a JSON-RPC call to get the address.
getBalance - A function that takes a provider and will make a JSON-RPC call to get the balance.
The wallet function must return a Promise that resolves to an object that has the following properties:
provider - the JavaScript provider for this wallet. [required]
instance - for SDK wallets instances that are separate from the provider. [optional]
interface -  a walletInterface or null if the user's current provider is not this wallet (for extension and mobile wallets). [required]
walletInterface
An abstraction built on top of an Ethereum JavaScript provider allowing interoperability with wallets and providers of any architecture. A valid walletInterface implements the following methods and attributes: 
name - The name of the wallet. [string][required]
connect - A function that requests account access and returns a Promise that resolves or rejects once the user confirms or rejects the request. [function][optional]
disconnect - A function to clean up / destroy any instances (mostly for SDK wallets). Will be called when a new wallet has been selected. [function][optional]
loading - A function that returns a Promise that resolves when the wallet has finished loading. This is to show a loading spinner as the wallet popup is loading (mostly for SDK wallets). [function][optional]
address - A stateSyncer object (see below for details). The get function on this stateSyncer must return a string which is the wallet address.
network - A stateSyncer object (see below for details). The get function on this stateSyncer must return a number which is the wallet network id.
balance - A stateSyncer object (see below for details). The get function on this stateSyncer must return a string which is the wallet address balance.
stateSyncer
An object that has either a get function or a onChange function and is used to keep user state in sync. The onChange method is preferred as it doesn't require background polling to keep in sync.
The get function returns a promise that resolves with a value. 
The onChange function takes a setState function as an argument and is used to set the state. Often it is needed to use the setState function to set the initial state and then register it to be called every time it changes.
iconSrc - [string][optional]
A source for the wallet logo icon.
iconSrcSet - [string][optional]
A source for the hi-res wallet logo icon.