Fetch last 10 blocks using Alchemy Transfers API

Question

could someone please elaborate on: fromBlock: the starting time range we want to fetch NFT mints over (defaults to latest)

I tried to pass a block but its not working... I have also seen fromBlock": "0x0" but not sure what 0x0 stands for...

I would like to fetch the last 10 blocks or so.

I am referring to: https://docs.alchemy.com/alchemy/enhanced-apis/transfers-api#alchemy_getassettransfers=

Answer 1

Alchemist here 💙

To fetch all NFT mint events within the last 10 blocks, you can use:

1. ethers.js to fetch block num, and then
2. use the Alchemy getAssetTransfers request to search "erc721" and "erc1155" transfers that have a fromAddress set to the null address, to filter for "mint events"

Here's an example script, you just need to swap out "your-api-key" with your Alchemy API key (sign up here if you don't have one).

import fetch, {Headers} from 'node-fetch';
import {ethers} from 'ethers';

// TODO: replace with your Alchemy API key
const API_KEY = "your-api-key";
const alchemy = new ethers.providers.AlchemyProvider("homestead", API_KEY);

// Get block range
const currentBlock = await alchemy.getBlockNumber();
const tenBlocksAgo = currentBlock - 10;
console.log("currentBlock:", currentBlock);
console.log("currentBlock (hex):", ethers.utils.hexlify(currentBlock));
console.log("10 blocks ago:", tenBlocksAgo);
console.log("10 blocks ago (hex):", ethers.utils.hexlify(tenBlocksAgo));

// Create alchemy getAssetTransfers request body
var requestBody = JSON.stringify({
  "jsonrpc": "2.0",
  "id": 0,
  "method": "alchemy_getAssetTransfers",
  "params": [
    {
      "fromBlock": ethers.utils.hexlify(tenBlocksAgo),
      "excludeZeroValue": true,
      "category": ["external", "erc721", "erc1155"],
      "fromAddress": "0x0000000000000000000000000000000000000000"
    }
  ]
});

// Construct the fetch request
var myHeaders = new Headers();
myHeaders.append("Content-Type", "application/json");

var requestOptions = {
  method: 'POST',
  headers: myHeaders,
  body: requestBody,
  redirect: 'follow'
};

// Fetch and print
fetch(`https://eth-mainnet.alchemyapi.io/v2/${API_KEY}`, requestOptions)
  .then(response => response.text())
  .then(result => console.log(result))
  .catch(error => console.log('error', error));

Hope that helps!