A lightweight JavaScript sdk to connect to the Blocknative backend Ethereum node infrastructure via a websocket connection for realtime transaction updates.
npm install bnc-sdk
importWebSocketfrom'ws'importBlocknativeSdkfrom'bnc-sdk'importWeb3from'web3'constweb3=newWeb3('<ws://some.local-or-remote.node:8546>')// create options objectconstoptions={dappId: '<YOUR_API_KEY>',networkId: 4,ws: WebSocket// un-comment if you would like to log all transaction events// transactionHandlers: [event => console.log(event.transaction)]}// initialize and connect to the apiconstblocknative=newBlocknativeSdk(options)consttxOptions={to: '0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D',value: 1000000000000000}// initiate a transaction via web3.jsweb3.eth.sendTransaction(txOptions).on('transactionHash',hash=>{// call with the transaction hash of the transaction that you would like to receive status updates forconst{ emitter }=blocknative.transaction(hash)// listen to some eventsemitter.on('txPool',transaction=>{console.log(`Sending ${transaction.value} wei to ${transaction.to}`)})emitter.on('txConfirmed',transaction=>{console.log('Transaction is confirmed!')})// catch every other event that occurs and log itemitter.on('all',transaction=>{console.log(`Transaction event: ${transaction.eventCode}`)})})importWebSocketfrom'ws'importBlocknativeSdkfrom'bnc-sdk'importWeb3from'web3'constweb3=newWeb3('<ws://some.local-or-remote.node:8546>')// create options objectconstoptions={dappId: '<YOUR_API_KEY>',networkId: 4,ws: WebSocket// un-comment if you would like to log all transaction events// transactionHandlers: [event => console.log(event.transaction)]}// initialize and connect to the apiconstblocknative=newBlocknativeSdk(options)constaddress='0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D'const{ emitter, details }=blocknative.account(address)emitter.on('all',transaction=>{console.log(transaction)})importBlocknativeSdkfrom'bnc-sdk'importWeb3from'web3'constweb3=newWeb3(window.ethereum)// create options objectconstoptions={dappId: '<YOUR_API_KEY>',networkId: 4// un-comment if you would like to log all transaction events// transactionHandlers: [event => console.log(event.transaction)]}// initialize and connect to the apiconstblocknative=newBlocknativeSdk(options)consttxOptions={to: '0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D',value: 1000000000000000}// initiate a transaction via web3.jsweb3.eth.sendTransaction(txOptions).on('transactionHash',hash=>{// call with the transaction hash of the transaction that you would like to receive status updates forconst{ emitter }=blocknative.transaction(hash)// listen to some eventsemitter.on('txPool',transaction=>{console.log(`Sending ${transaction.value} wei to ${transaction.to}`)})emitter.on('txConfirmed',transaction=>{console.log('Transaction is confirmed!')})// catch every other event that occurs and log itemitter.on('all',transaction=>{console.log(`Transaction event: ${transaction.eventCode}`)})})Transaction Preview lets you preview the outputs of any custom transactions that you submit to it. By harnessing the power of our network of Ethereum nodes, with our existing decoding and transaction lifecycle knowledge, we hope to give users of Transaction Preview even greater comfort when interacting in the Web3 space. Previewing a transaction is particularly useful for: Wallets: Help users preview net-balance changes & identify malicious contract behavior or buggy smart contracts before interacting with them. DEXs & Swaps: Report accurate slippage, Accurate tokens received, and accurate failing calls Traders: Preview many iterations of the same trade and execute only the most profitable one Lending Protocols: Tell whether a Borrow / Repay / Claim transaction will go through Auctions: Tell whether your bid or listing will go through and its accuracy & effects NFTs: Tell whether your NFT mint, purchase, or transfer will go through & much more without spending a single wei in gas!
Transaction Preview is currently only supported for Ethereum: Main. Please stay tuned for its availability on other networks supported by Blocknative.
Usage rate limit for the Transaction Preview API is 100 requests per 60-second window. Transaction Preview consumes the same daily limits on your Blocknative plan as pending simulated transactions in Simulation Platform. You can view your current consumption on your Blocknative Account Page.
This example will mock a contract interaction between two wallets.
importBlocknativeSdk,{SimulationTransaction,MultiSimOutput}from'bnc-sdk'import{SimulationTransaction,MultiSimOutput}from'bnc-sdk'import{ethers}from'ethers'constaddressFrom='0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045'constCONTRACT_ADDRESS='0x7a250d5630b4cf539739df2c5dacb4c659f2488d'consterc20_interface=['function approve(address _spender, uint256 _value) public returns (bool success)','function transferFrom(address sender, address recipient, uint256 amount) external returns (bool)','function balanceOf(address owner) view returns (uint256)']constuniswapV2router_interface=['function swapExactTokensForETH(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline) external returns (uint[] memory amounts)']constweth='0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2'constdai='0x6B175474E89094C44Da98b954EedeAC495271d0F'letswapTxDataletapproveTxDataconstcreateTransaction=async()=>{constswapContract=newethers.Contract(CONTRACT_ADDRESS,uniswapV2router_interface)consterc20_contract=newethers.Contract(weth,erc20_interface)constoneEther=ethers.BigNumber.from('1591000000000000000000')approveTxData=awaiterc20_contract.populateTransaction.approve(CONTRACT_ADDRESS,oneEther)constamountOutMin=0constamountOutMinHex=ethers.BigNumber.from(amountOutMin.toString())._hexconstpath=[dai,weth]constdeadline=Math.floor(Date.now()/1000)+60*1// 1 minutes from the current Unix timeconstinputAmountHex=oneEther.toHexString()swapTxData=awaitswapContract.populateTransaction.swapExactTokensForETH(inputAmountHex,amountOutMinHex,path,addressFrom,deadline)}awaitcreateTransaction()constaccount_address='0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045'constuniswapV2Router='0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D'conststubTrans=[{from: account_address,to: dai,input: approveTxData.data,gas: 1000000,gasPrice: 48000000000,value: 0},{from: account_address,to: uniswapV2Router,input: swapTxData.data,gas: 1000000,gasPrice: 48000000000,value: 0}]// create options objectconstoptions={dappId: '<YOUR_API_KEY>',networkId: 1}// initialize and connect to the apiconstblocknativeSDK=newBlocknativeSdk(options)constsingleSim: Promise<SimulationTransactionOutput>=blocknativeSDK.simulate('ethereum','main',stubTrans[1])constmultiSim: Promise<MultiSimOutput>=blocknativeSDK.multiSim(stubTrans)importBlocknativeSdkfrom'bnc-sdk'importWeb3from'web3'constweb3=newWeb3(window.ethereum)// create options objectconstoptions={dappId: '<YOUR_API_KEY>',networkId: 4// un-comment if you would like to log all transaction events// transactionHandlers: [event => console.log(event.transaction)]}// initialize and connect to the apiconstblocknative=newBlocknativeSdk(options)constaddress='0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D'const{ emitter, details }=blocknative.account(address)emitter.on('all',transaction=>{console.log(transaction)})For detailed documentation head to docs.blocknative.com
For apps that operate on multiple chains at once, you can use the Multichain SDK which provides a simple interface that abstracts away handling multiple WS connections at once and has a new API for subscribing to events.
Currently a transaction hash or account address can be subscribed to for all events. The subscribe method requires an id, chainId and a type and returns an Observable. The Observable that is returned is specific for events on this subscription and on completion or unsubscribing from the observable will automatically unsubscribe within the SDK. Alternatively you can listen on the global transactions Observable at sdk.transactions$.
importBlocknativefrom'bnc-sdk'constblocknative=Blocknative.multichain({apiKey: '<YOUR_API_KEY>'})// subscribe to address eventsconstaddressSubscription=blocknative.subscribe({id: '0x32ee303b76B27A1cd1013DE2eA4513aceB937c72',chainId: '0x1',type: 'account'})// can listen to the address subscription directlyaddressSubscription.subscribe(transaction=>console.log(transaction))// subscribe to transaction eventsconsttransactionSubscription=blocknative.subscribe({id: '0xbb1af436fd539a6282c6f45ed900abb5ac95ec435367f61fa8815a61bd2a7211',chainId: '0x1',type: 'transaction'})// can listen to the transaction subscription directlytransactionSubscription.subscribe(transaction=>console.log(transaction))// or can listen for all transaction events on the global transactions$ observableblocknative.transaction$.subscribe(transaction=>console.log(transaction))To stop listening to events on a transaction hash or account address, call the unsubscribe method. If called without a chainId, all networks will unsubscribe from the transaction or address. To only unsubscribe on a particular network, pass in the chainId of that network.
blocknative.unsubscribe({id: 'transactionHashOrAddress',chainId: '0x1'})