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Getting Started

In this tutorial, you will use ZeroDev to send gasless transactions and bundle transactions.

Create a project​

Go to the ZeroDev dashboard and create a project for Polygon Mumbai.

Note that your project has an ID. We will be using this ID in one of the later steps.

Set up gas policies​

While we are at the dashboard, let's set up "Gas Policies" -- rules that determine which transactions we will sponsor gas for.

Go to the "Gas Policies" section of your dashboard and create a new "Project Policy":

Here we are saying that we will sponsor up to 100 transactions per minute.

Install dependencies​

info

For Node.js we recommend v18 or above. Lower Node.js versions have not been tested.

Create an empty working directory and initialize it with npm:

mkdir zerodev-tutorial
cd zerodev-tutorial
npm init -y

Then install the ZeroDev SDK:

npm i @zerodev/sdk

Send gasless transactions​

We will now implement a simple script that:

  1. Creates an AA wallet from a private key
  2. Mints an NFT without paying gas

To make things easier, we already deployed an NFT contract on Polygon Mumbai that allows anyone to mint NFTs.

Create a file app.js with the following content:

const { ECDSAProvider } = require('@zerodev/sdk')
const { LocalAccountSigner } = require("@alchemy/aa-core")
const { encodeFunctionData, parseAbi, createPublicClient, http } = require('viem')
const { polygonMumbai } = require('viem/chains')

// ZeroDev Project ID
const projectId = process.env.PROJECT_ID

// The "owner" of the AA wallet, which in this case is a private key
const owner = LocalAccountSigner.privateKeyToAccountSigner(process.env.PRIVATE_KEY)

// The NFT contract we will be interacting with
const contractAddress = '0x34bE7f35132E97915633BC1fc020364EA5134863'
const contractABI = parseAbi([
  'function mint(address _to) public',
  'function balanceOf(address owner) external view returns (uint256 balance)'
])
const publicClient = createPublicClient({
  chain: polygonMumbai,
  // the API is rate limited and for demo purposes only
  // in production, replace this with your own node provider (e.g. Infura/Alchemy)
  transport: http('https://polygon-mumbai.infura.io/v3/f36f7f706a58477884ce6fe89165666c'),
})

const main = async () => {
  // Create the AA wallet
  const ecdsaProvider = await ECDSAProvider.init({
    projectId,
    owner,
  })
  const address = await ecdsaProvider.getAddress()
  console.log('My address:', address)

  // Mint the NFT
  const { hash } = await ecdsaProvider.sendUserOperation({
    target: contractAddress,
    data: encodeFunctionData({
      abi: contractABI,
      functionName: 'mint',
      args: [address],
    }),
  })
  await ecdsaProvider.waitForUserOperationTransaction(hash)

  // Check how many NFTs we have
  const balanceOf = await publicClient.readContract({
    address: contractAddress,
    abi: contractABI,
    functionName: 'balanceOf',
    args: [address],
  })
  console.log(`NFT balance: ${balanceOf}`)
}

main().then(() => process.exit(0))

Feel free to read the script and see what it's doing. It should be fairly straightforward. Note that:

  • We are using the ZeroDev SDK with Viem in this example, but you can use it with Ethers as well.
  • A transaction from an AA wallet is also known as a "user operation," which is why we use the function sendUserOperation to send the transaction.

The script requires that we set a project ID and a private key. We can generate a random private key with this command:

node -e "console.log('0x' + require('crypto').randomBytes(32).toString('hex'))"

Then export the variables:

export PROJECT_ID="your project ID"
export PRIVATE_KEY="your private key"

Make sure to replace the values with your actual project ID and the private key you just generated.

Now run this script:

node app.js

If everything goes well, you should see output like:

My address:  0xdc25579151367F44a99E9e92D1E4237200A32Cba
NFT balance: 1

Boom! You just sent a your first gasless AA transaction. You can go to the block explorer and search for your address, and you should see a transaction under the ERC-721 Token Txns section, even though your wallet has no gas. Magical!

info

You might wonder why you don't see any transactions in the block explorer. This is because a ERC-4337 transaction is not a regular transaction. To see your transactions, use a ERC-4337 explorer such as JiffyScan.

Note how our account is identified as a "contract" by the block explorer. This is because in account abstraction, all accounts are smart contract accounts.

Feel free to run the script a few more times to mint more NFTs. It's free after all :)

Bundle transactions​

Minting one NFT at a time is cool, but what if we wanna mint two at a time? With a traditional wallet, you'd have to send two transactions. With AA, we can bundle multiple transactions and send them as one -- saving the user time and gas.

To mint two NFTs at a time, simply replace this block:

  const { hash } = await ecdsaProvider.sendUserOperation([{
    target: contractAddress,
    data: encodeFunctionData({
      abi: contractABI,
      functionName: 'mint',
      args: [address],
    }),
  }])

With this block (passing two UserOperations as an array):

  const userOp = {
    target: contractAddress,
    data: encodeFunctionData({
      abi: contractABI,
      functionName: 'mint',
      args: [address],
    }),
  }
  const { hash } = await ecdsaProvider.sendUserOperation([userOp, userOp])

Now, run node app.js again. You should see that your NFT balance is now increasing two at a time!

Next Steps​

Now that you have got a taste of ZeroDev, it's time to dive deep into the docs!