Getting started

Getting started with the Hop v2 JavaScript SDK

Install module

Using NPM:

npm install @hop-protocol/v2-sdk

Using Yarn:

yarn add @hop-protocol/v2-sdk

CDN

jsDeliver CDN:

<script src="https://cdn.jsdelivr.net/npm/@hop-protocol/v2-sdk@latest/hop.js"></script>

unpkg CDN:

<script src="https://unpkg.com/@hop-protocol/v2-sdk@latest/hop.js"></script>

Import module

Import as ES6 module (e.g. Using TypeScript, babel, webpack):

import { Hop } from '@hop-protocol/v2-sdk'

Import as commonJS module (e.g. Using Node.js directly or no ES6 modules):

const { Hop } = require('@hop-protocol/v2-sdk')

Instantiate SDK

import { Hop } from '@hop-protocol/v2-sdk'

const hop = new Hop({ network: 'sepolia' })

Avaiable networks are only sepolia at this time.

Hop V2 SDK Documentation

The Hop V2 SDK provides a simple interface for interacting with the Hop Protocol V2. This documentation will help you get started with integrating the SDK into your application.

Table of Contents

• Installation

• SDK Setup

• Complete Transfer Flow

  • 1. Initialize SDK

  • 2. Check Token Approval

  • 3. Send Tokens

  • 4. Monitor Transfer Status

  • 5. Handle Transfer Completion

• Additional Functions

• Event Handling

• Types

• Best Practices

Installation

npm install @hop-protocol/v2-sdk

SDK Setup

First, initialize the SDK with your network configuration:

import { Hop } from '@hop-protocol/v2-sdk'
import { providers } from 'ethers'

const hop = new Hop({
  network: 'mainnet', // or 'sepolia' for testnet
  signersOrProviders: {
    '1': new providers.JsonRpcProvider('ETHEREUM_RPC_URL'),
    '10': new providers.JsonRpcProvider('OPTIMISM_RPC_URL'),
    // Add other chains as needed
  }
})

Constructor Options

Parameter	Type	Description	Required
network	string	Network name ('mainnet' or 'sepolia')	No
signersOrProviders	SignersOrProviders	Map of chain IDs to ethers signers/providers	Yes
contractAddresses	Addresses	Custom contract addresses	No
batchBlocks	number	Number of blocks to batch in queries	No

Complete Transfer Flow

Let's walk through the complete process of transferring tokens from one chain to another.

1. Initialize SDK

First, set up your connection and token details:

// Token addresses on respective chains
const sourceToken = '0x...'  // Token on source chain
const destToken = '0x...'    // Token on destination chain
const amount = '1000000000000000000' // Amount in wei (1 token with 18 decimals)
const recipient = '0x...'    // Recipient address

// Chain IDs
const fromChainId = '1'      // Ethereum
const toChainId = '10'       // Optimism

2. Check Token Approval

Before sending tokens, check if approval is needed:

// Check if approval is needed
const needsApproval = await hop.getNeedsApprovalForSendTokens({
  fromChainId,
  toChainId,
  fromToken: sourceToken,
  toToken: destToken,
  amount,
  account: senderAddress
})

if (needsApproval) {
  // Approve tokens
  const approveTx = await hop.approveSendTokens({
    fromChainId,
    toChainId,
    fromToken: sourceToken,
    toToken: destToken,
    amount
  })
  
  // Wait for approval transaction
  await approveTx.wait()
}

3. Send Tokens

Calculate fees and send the tokens:

// Get the estimated received amount and fees
const sendData = await hop.getSendData({
  fromChainId,
  toChainId,
  fromToken: sourceToken,
  toToken: destToken,
  amount,
  minAmountOut: '0' // We'll calculate this based on slippage
})

// Calculate minAmountOut with 1% slippage
const slippageTolerance = 0.01 // 1%
const minAmountOut = hop.calcAmountOutMin({
  amountOut: sendData.amountOut,
  slippageTolerance
})

// Send tokens
const tx = await hop.sendTokens({
  fromChainId,
  toChainId,
  fromToken: sourceToken,
  toToken: destToken,
  amount,
  to: recipient,
  minAmountOut
})

// Wait for transaction confirmation
const receipt = await tx.wait()
console.log('Send transaction hash:', receipt.transactionHash)

4. Monitor Transfer Status

After sending tokens, monitor the transfer status:

// Get transfer ID from transaction hash
const transferId = await hop.getTransferIdFromTransactionHash({
  chainId: fromChainId,
  transactionHash: receipt.transactionHash
})

// Monitor status
async function checkTransferStatus() {
  const status = await hop.getTransferStatus({
    transferId,
    fromChainId,
    toChainId
  })

  switch (status.state) {
    case 'PendingBond':
      console.log('Transfer pending bonding...')
      return false
    case 'Bonded':
      console.log('Transfer completed!')
      return true
    case 'NotFound':
      console.log('Transfer not found')
      return false
  }
}

// Poll for status (implement your own polling mechanism)
const interval = setInterval(async () => {
  const isComplete = await checkTransferStatus()
  if (isComplete) {
    clearInterval(interval)
  }
}, 5000)

5. Handle Transfer Completion

The transfer can complete in two ways:

Option A: Bonded Transfer (Automatic)

If a bonder picks up your transfer, it will automatically be completed on the destination chain. The status will change to 'Bonded'.

Option B: Manual Claim (If not bonded)

If the transfer isn't bonded after some time, you can manually claim it:

// First, push the claim if needed
const pushClaimTx = await hop.pushClaim({
  transferId,
  fromChainId,
  toChainId
})
await pushClaimTx.wait()

// Then withdraw the claim
const withdrawClaimTx = await hop.withdrawClaim({
  transferId,
  fromChainId,
  toChainId
})
await withdrawClaimTx.wait()

Additional Functions

Calculate Fees

// Get send fee
const fee = await hop.getSendFee({
  fromChainId,
  toChainId,
  fromToken: sourceToken,
  toToken: destToken
})

// Get max bonder fee
const maxBonderFee = await hop.getMaxBonderFee({
  amountIn: amount
})

Estimate Gas

const gasCost = await hop.estimateGasCostForSend({
  from: senderAddress,
  fromChainId,
  toChainId,
  fromToken: sourceToken,
  toToken: destToken,
  amount,
  minAmountOut
})

Event Handling

Monitor transfer-related events:

// Listen for TransferSent events
const events = await hop.getEvents({
  eventName: 'TransferSent',
  chainId: fromChainId,
  fromBlock: receipt.blockNumber,
  toBlock: 'latest'
})

// Listen for TransferBonded events
const bondedEvents = await hop.getEvents({
  eventName: 'TransferBonded',
  chainId: toChainId,
  fromBlock: receipt.blockNumber,
  toBlock: 'latest'
})

Types

Key types for transfer operations:

enum TransferState {
  PendingBond = 'PendingBond',
  Bonded = 'Bonded',
  NotFound = 'NotFound'
}

type SendData = {
  amountIn: BigNumber
  amountOut: BigNumber
  estimatedReceived: BigNumber
  sendFee: BigNumber
  maxBonderFee: BigNumber
  routeChainIds: string[]
}

More examples

If you'd like to see more examples or have any feedback, message us on Discord!

SDK API Reference

API Reference

Contract addresses

Contract Addresses