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WTF Ethers: 16. Batch Collect

I've been revisiting ethers.js recently to refresh my understanding of the details and to write a simple tutorial called "WTF Ethers" for beginners.

Twitter: @0xAA_Science

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All the code and tutorials are open-sourced on GitHub:

In this session, we will introduce how to use ethers.js to collect the assets of multiple wallets (ETH and tokens) into one wallet.

Batch Collect

After interacting and playing around with the chain, we need to consolidate and manage the assets of multiple wallets. You can use HD Wallet or other methods to operate multiple wallets with different private keys, and then use the ethers.js script to complete the collection. Below, we will demonstrate the collection of ETH (native token) and WETH (ERC20 token) separately.

  1. Create a provider and a wallet, where wallet is the receiving wallet for the assets.

    // Prepare Alchemy API, you can refer to 
    const ALCHEMY_GOERLI_URL = '';
    const provider = new ethers.JsonRpcProvider(ALCHEMY_GOERLI_URL);
    // Create wallet object using private key and provider
    const privateKey = '0x21ac72b6ce19661adf31ef0d2bf8c3fcad003deee3dc1a1a64f5fa3d6b049c06'
    const wallet = new ethers.Wallet(privateKey, provider)
  2. Declare the WETH contract.

    // WETH ABI
    const abiWETH = [
    "function balanceOf(address) public view returns(uint)",
    "function transfer(address, uint) public returns (bool)",
    // WETH contract address (Goerli testnet)
    const addressWETH = '0xB4FBF271143F4FBf7B91A5ded31805e42b2208d6' // WETH Contract
    // Declare the WETH contract
    const contractWETH = new ethers.Contract(addressWETH, abiWETH, wallet)
  3. Create an HD wallet to manage multiple wallets.

    console.log("\n1. Create HD wallet")
    // Generate HD wallet from mnemonic
    const mnemonic = `air organ twist rule prison symptom jazz cheap rather dizzy verb glare jeans orbit weapon universe require tired sing casino business anxiety seminar hunt`
    const hdNode = ethers.HDNodeWallet.fromPhrase(mnemonic)

    HD Wallet

  4. Derive 20 wallets from the HD wallet, and these wallets should have assets.

    const numWallet = 20
    // Derivation path: m / purpose' / coin_type' / account' / change / address_index
    // We only need to switch the last address_index to derive a new wallet from hdNode
    let basePath = "m/44'/60'/0'/0";
    let wallets = [];
    for (let i = 0; i < numWallet; i++) {
    let hdNodeNew = hdNode.derivePath(basePath + "/" + i);
    let walletNew = new ethers.Wallet(hdNodeNew.privateKey);
    // Define the amount to send
    const amount = ethers.parseEther("0.0001")
    console.log(`Amount to send: ${amount}`)

    Generate 20 addresses

  5. Read the ETH and WETH balance of an address.

    console.log("\n3. Read the ETH and WETH balance of an address")
    // Read the WETH balance
    const balanceWETH = await contractWETH.balanceOf(wallets[19])
    console.log(`WETH balance: ${ethersfromPhrase.formatEther(balanceWETH)}`)
    // Read the ETH balance
    const balanceETH = await provider.getBalance(wallets[19])
    console.log(`ETH balance: ${ethersfromPhrase.formatEther(balanceETH)}\n`)

    Read balances

  6. Use the sendTransaction() method of the wallet class to send transactions and collect ETH from each wallet.

    // 6. Batch collect ETH from wallets
    console.log("\n4. Batch collect ETH from 20 wallets")
    const txSendETH = {
    to: wallet.address,
    value: amount
    for (let i = 0; i < numWallet; i++) {
    // Connect the wallet to the provider
    let walletiWithProvider = wallets[i].connect(provider)
    var tx = await walletiWithProvider.sendTransaction(txSendETH)
    console.log(`Collecting ETH from wallet ${i+1} ${walletiWithProvider.address}`)
    await tx.wait()
    console.log(`ETH collection completed`)

    Collect ETH

  7. Connect the WETH contract to the new wallet and call the transfer() method to collect WETH from each wallet.

    for (let i = 0; i < numWallet; i++) {
    // Connect the wallet to the provider
    let walletiWithProvider = wallets[i].connect(provider)
    // Connect the contract to the new wallet
    let contractConnected = contractWETH.connect(walletiWithProvider)
    var tx = await contractConnected.transfer(wallet.address, amount)
    console.log(`The ${i+1}th wallet ${wallets[i].address} WETH collection starts`)
    await tx.wait()
    console.log(`WETH collection ends`)

WETH collection

  1. Read the post-collection ETH and WETH balance of an address, and you can see the decrease in ETH and WETH balances, collection succeeded!
    console.log("\n6. Read the post-collection ETH and WETH balance of an address")
    // Read WETH balance
    const balanceWETHAfter = await contractWETH.balanceOf(wallets[19])
    console.log(`WETH holdings after collection: ${ethersfromPhrase.formatEther(balanceWETHAfter)}`)
    // Read ETH balance
    const balanceETHAfter = await provider.getBalance(wallets[19])
    console.log(`ETH holdings after collection: ${ethersfromPhrase.formatEther(balanceETHAfter)}\n`)

Changes in balances after collection


In this lecture, we introduced batch collect and used ethers.js scripts to collect ETH and WETH from 20 wallets into one wallet.