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Takes care of onboarding your users, keeping them informed about transaction status and comprehensive usage analytics with minimal setup. Supports web3.js versions 0.20 and 1.0.

note: web3.js 1.0.0 beta versions 38, 39, 40, 41, 42, 43, 44, 45 have bugs when interacting with MetaMask, we recommend you avoid these versions of web3.js


Assist's UI elements

☝️ A collection of Assist's UI elements.

👇 Assist's transaction notifications in action.

Assist's transaction notifications

Getting Started

To integrate Assist.js into your dapp, you'll need to do 5 things:

  1. Create a free account and get an API key from
  2. Install the widget
  3. Initialize the library
  4. Call onboard
  5. Decorate your contracts

Install the widget


npm i bnc-assist


yarn add bnc-assist

Script Tag

The library uses semantic versioning. The current version is 0.8.0. There are minified and non-minified versions. Put this script at the top of your <head>

<script src=""></script>

<!-- OR... -->

<script src=""></script>

Initialize the Library

Full documentation of the config object is below, but the minimum required config is as follows:

var bncAssistConfig = {
  dappId: apiKey,       // [String] The API key created on

  networkId: networkId  // [Integer] The network ID of the Ethereum network your dapp is deployd on.
                        //           See below for instructions on how to setup for local blockchains.

var assistInstance = assist.init(bncAssistConfig);

Call onboard

At some point in your dapp's workflow, you'll want to ensure users are within an environment which will allow them to make transactions, such as a browser with MetaMask, unlocked wallet, etc. This is done by calling onboard. Some dapps might want to call onboard immediately upon any page load. Others may wait until loading certain pages or until a certain button is clicked. In any event, it is as simple as calling:

  .then(function(state) {
    // User has been successfully onboarded and is ready to transact
    // Will resolve with the current state of the user
    // This means we can be sure of the follwing user properties:
    //  - They are using a compatible browser
    //  - They have a web3-enabled wallet installed
    //  - The wallet is connected to the config-specified networkId
    //  - The wallet is unlocked and contains at least `minimumBalance` in wei
    //  - They have connected their wallet to the dapp, congruent with EIP1102
  .catch(function(state) {
    // The user exited onboarding before completion
    // Will let you know what stage of onboarding the user was up to when they exited via the state object

Decorate Your Contracts

The first three steps in the getting started flow will get your users onboarded. This step adds transaction support in order to help guide your users through a series of issues that can arise when signing transactions.

Using our decorated contracts will also enable some anonymized transaction-level metrics to give you insights into things including but not limited to:

  • How many transactions fail because a user doesn't have enough Ether
  • How many transactions are started but rejected by the user
  • How many users come to your dapp without a web3 wallet

Decorating your contracts is simple:

var myContract = new web3.eth.Contract(abi, address)
var myDecoratedContract = assistInstance.Contract(myContract)

// and then replace `myContract` with `myDecoratedContract`
// throughout your app
// ...

You can then use myDecoratedContract instead of myContract.

To speed things up, you can decorate the contract inline:

var myContract = assistInstance.Contract(new web3.eth.Contract(abi, address))


If using web3 versions 1.0 and you would like to listen for the events triggered on the promiEvent that is normally returned from a transaction call, Assist returns the promiEvent, but it is wrapped in an object to prevent it from resolving internally in Assist.

const { promiEvent } = await decoratedContract.myMethod(param).send(txOptions)

promiEvent.on('receipt', () => {
  // ...

API Reference


A JavaScript Object that is passed to the init function. Default values are in [square brackets] where they are set by Assist.js.

var config = {
  networkId: Number, // The network id of the Ethereum network your dapp is working with (REQUIRED)
  dappId: String, // The API key supplied to you by Blocknative (REQUIRED)
  web3: Object, // The instantiated version of web3 that the dapp is using
  mobileBlocked: Boolean, // Defines if the dapp works on mobile [false]
  minimumBalance: String, // Defines the minimum balance in Wei that a user needs to have to use the dapp [0]
  headlessMode: Boolean, // Turn off Assist UI, but still retain analytics collection [false]
  messages: {
    // See custom transaction messages section below for more details
    txRequest: Function, // Transaction request has been initiated and is awaiting user approval
    txSent: Function, // Transaction has been sent to the network
    txPending: Function, // Transaction is pending and has been detected in the mempool
    txSendFail: Function, // Transaction failed to be sent to the network
    txStall: Function, // Transaction was sent but not received in the mempool after 30 secs
    txFailed: Function, // Transaction failed
    nsfFail: Function, // User doesn't have enough funds to complete transaction
    txRepeat: Function, // Warning to user that they might be repeating a transaction
    txAwaitingApproval: Function, // Warning to the user that they have a previous transaction awaiting approval
    txConfirmReminder: Function, // A warning to the user that their current transaction is still awaiting approval
    txConfirmed: Function, // Transaction is confirmed
    txSpeedUp: Function // The user has re-submitted a transaction with a higher gas price
  images: {
    welcome: {
      src: String, // Image URL for welcome onboard modal
      srcset: String // Image URL(s) for welcome onboard modal
    complete: {
      src: String, // Image URL for complete onboard modal
      srcset: String // Image URL(s) for complete onboard modal
  style: {
    darkMode: Boolean, // Set Assist UI to dark mode
    notificationsPosition: String, // Defines which corner transaction notifications will be positioned. Options: 'topLeft', 'topRight', 'bottomRight', 'bottomLeft'. ['bottomRight']
    css: String // Custom css string to overide Assist default styles
  truffleContract: Boolean, // Set to true if contract object has been instantiated with truffle-contract [false]

Custom Transaction Messages

Custom transaction messages can be set to override the default messages Assist provides. To do this you provide callback functions for each eventCode that you want to override. The callback functions must return a String and will be called with the following object to provide context information about the transaction:

  transaction: {
    to: String, // The address the transaction is going to
    gas: String, // Gas (wei)
    gasPrice: String, // Gas price (wei)
    hash: String, // The transaction hash
    nonce: Number, // The transaction nonce
    value: String // The value of the transaction (wei)
  contract: {
    // This object will be undefined if it is not a contract transaction
    methodName: String, // The name of the method that was called
    parameters: Array // The parameters that the method was called with

You can provide a messages object to the config to set global message overrides. Each callback can parse the context object that is passed to it and decide what to return or just return a standard message for each eventCode:

var config = {
  messages: {
    txSent: function(data) {
      return 'Your transaction has been sent to the network'
    txConfirmed: function(data) {
      if (data.contract.methodName === 'contribute') {
        return 'Congratulations! You are now a contributor to the campaign'
    // ....

Sometimes you want more granular control over the transaction messages and you have all the relevant information you need to create a custom transaction message at the time of calling the method. In that case you can also add custom transactions messages inline with your transaction calls which take precedent over the messages set globally in the config.


// 0.2 style send, param2, options, callback, {messages: {txPending: () => `Voting for ${param1} in progress`}})

// 1.0 style send, param2).send(options, {messages: {txPending: () => `Voting for ${param1} in progress`}})

The messages object must always be the last argument provided to the send method for it to be recognized.

Ethereum Network Ids

The available ids for the networkId property of the config object:

  • 1: mainnet
  • 3: ropsten testnet
  • 4: rinkeby testnet

The kovan testnet is not supported.

Local Networks

When you are running locally (e.g. using ganache), set networkId in the config to the network id that the local network is set to. Any number that is not 1, 3, 4 and 42 is valid and will be recognized as a local network. If using the Ganache CLI you can set the network id via the --networkId option.


Assist keeps track of the current state of the user environment as a JavaScript Object

state = {
  mobileDevice: Boolean, // User is on a mobile device
  validBrowser: Boolean, // User is on a valid web3 browser
  currentProvider: String, // Current provider being used to connect to the network
  web3Wallet: Boolean, // User has a web3Wallet installed
  accessToAccounts: Boolean, // Dapp has access to accounts
  walletLoggedIn: Boolean, // User is logged in to wallet
  walletEnabled: Boolean, // User has enabled EIP 1102 compliant wallet
  accountAddress: String, // Address of the user's selected account
  accountBalance: String, // User account balance
  minimumBalance: String, // User has the minimum balance specified in the config
  userCurrentNetworkId: Number, // Network id of the network the user is currently on
  correctNetwork: Boolean, // User is on the network specified in the config

The promises that are returned from calls to getState and onboard resolve and reject with this state object.


All errors are called with eventCode and message properties.


  eventCode: 'initFail',
  message: 'An API key is required to run Assist'

Error Codes

The following are the possible error codes from Assist.js.

initFail          - initialization of the library failed
mobileBlocked     - mobile browsers are blocked from accessing this dapp
browserFail       - browser is not compatible with web3.js wallets
walletFail        - user does not have a web3-enabled wallet installed
walletEnableFail  - user has not logged into their wallet
networkFail       - user's web3 wallet is not connected to the correct network
nsfFail           - user does not have enough funds in their wallet

Headless Mode

By default, Assist will create UI elements in your application at certain times to guide users. You can disable this feature and run Assist in "headless mode" by setting headlessMode: true in the config. This still enables you to collect analytics, but won't change the underlying behaviour of your application at all.

Mobile Dapps

Assist doesn't currently support mobile dapp browsers. If your dapp also doesn't support mobile browsers, setting mobileBlocked: true in the config will detect mobile user agents and show UI that will direct them to use a desktop browser instead. If your dapp does support mobile devices then Assist will be disabled and your transactions and contracts will work as normal. However if you call the onboard function when a user is on a mobile device, Assist will show a mobile not supported UI as onboarding isn't supported on mobile. So it is advised to check if a user is on a mobile device before calling onboard. Calling getState and referring to the mobileDevice property is an easy way of doing that.

Minimum Balance

By supplying an amount of wei to the minimumBalance option of the config, developers can limit access to their dapp to users who have at least this much Ether in their wallet.

Repeat Transactions

Assist will detect transactions which look to be repeated. We notify users of repeat transactions when we see sequential transactions with the same to address and the same value.




config - Object: Config object to configure and setup Assist (Required)


The initialized version of the Assist library


var assistInstance = assist.init(assistConfig)




  • resolves with state object
  • rejects with state object


  .then(function(state) {
    // User has been successfully onboarded and is ready to transact
  .catch(function(state) {
    // The user exited onboarding before completion



contractInstance - Object: Instantiated web3 contract object (Required)


A decorated contract to be used instead of the original instance


const myContract = new web3.eth.Contract(abi, address)
const myDecoratedContract = assistInstance.Contract(myContract)


Transaction(txObject [, callback])


txObject - Object: Transaction object (Required) callback - Function: Optional error first style callback if you don't want to use promises


Promise or PromiEvent (web3.js 1.0)

  • resolves with transaction hash
  • rejects with an error message


  .then(txHash => {
    // Transaction has been sent to the network
  .catch(error => {
    console.log(error.message) // => 'User has insufficient funds'




  • resolves with the state object that represents the current user environment


  .then(function(state) {
    if (state.validBrowser) {
      console.log('valid browser')



style - Object: Object containing new style information (Required)

const style = {
    darkMode: Boolean, // Set Assist UI to dark mode
    css: String, // Custom css string to overide Assist default styles
    notificationsPosition: String, // Defines which corner transaction notifications will be positioned. Options: 'topLeft', 'topRight', 'bottomRight', 'bottomLeft'. ['bottomRight']


// Enable dark mode
const style = {
  darkMode: true

// Disable dark mode and set notification background to black
const style = {
  darkMode: false,
  css: `.bn-notification { background: black }`

notify(type, message, options)

Trigger a custom UI notification


type - String: One of: ['success', 'pending', 'error'] (Required)

message - String: The message to display in the notification. HTML can be embedded in the string. (Required)

options - Object: Further customize the notification

options = {
  customTimeout: Number, // Specify how many ms the notification should exist. Set to -1 for no timeout.
  customCode: String // An identifier for this notify call

options.customTimeout defaults: { success: 2000, pending: 5000, error: 5000 }



  • a function that when called will dismiss the notification


// Display a success notification with an embedded link for 5000ms
assistInstance.notify('success', 'Operation was a success! Click <a href="" target="_blank">here</a> to view more', { customTimeout: 5000 });

// Display a pending notification, load data from an imaginary backend
// and dismiss the pending notification only when the data is loaded
const dismiss = assistInstance.notify('pending', 'Loading data...', { customTimeout: -1 });
myEventEmitter.on('data-from-backend-loaded', () => {


Installing Dependencies


npm i





npm test


yarn test



npm run build


yarn build

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