DetermineNFTOwnershipThroughEvents.js

const Web3 = require('web3');

// Initialize web3 instance
const web3 = new Web3('your rpc endpoint');

async function getNFTsOwnedByAddress(contractAddress, ownerAddress) {
    // Create a new contract instance
    const contract = new web3.eth.Contract([
        {
            "anonymous": false,
            "inputs": [
                {
                    "indexed": true,
                    "name": "from",
                    "type": "address"
                },
                {
                    "indexed": true,
                    "name": "to",
                    "type": "address"
                },
                {
                    "indexed": true,
                    "name": "tokenId",
                    "type": "uint256"
                }
            ],
            "name": "Transfer",
            "type": "event"
        }
    ], contractAddress);

		// THESE FILTERS QUERY FROM BLOCK 0 WHICH IS NOT EFFICIENT

    // Get past Transfer events for incoming transfers
    const incomingEvents = await contract.getPastEvents('Transfer', {
        filter: { to: ownerAddress },
        fromBlock: 0,
        toBlock: 'latest'
    });

    // Get past Transfer events for outgoing transfers
    const outgoingEvents = await contract.getPastEvents('Transfer', {
        filter: { from: ownerAddress },
        fromBlock: 0,
        toBlock: 'latest'
    });

    // Extract tokenIds from the events
    const incomingTokenIds = new Set(incomingEvents.map(event => event.returnValues.tokenId));
    const outgoingTokenIds = new Set(outgoingEvents.map(event => event.returnValues.tokenId));

    // Filter out the tokens that were transferred away
    const ownedTokenIds = [...incomingTokenIds].filter(tokenId => !outgoingTokenIds.has(tokenId));

    return ownedTokenIds;
}

// Usage
getNFTsOwnedByAddress('YOUR_CONTRACT_ADDRESS', 'TARGET_OWNER_ADDRESS')
    .then(tokenIds => console.log(tokenIds))
    .catch(err => console.error(err));