Alchemy Hello World

Alchemy Hello World

Overview

Minimal working examples with the real Alchemy SDK: get ETH balance, fetch NFTs for a wallet, read ERC-20 token balances, and subscribe to pending transactions.

Prerequisites

• Completed alchemy-install-auth setup
• alchemy-sdk installed (npm install alchemy-sdk)
• Valid API key configured

Instructions

Step 1: Get ETH Balance

// src/hello-world/get-balance.ts
import { Alchemy, Network, Utils } from 'alchemy-sdk';

const alchemy = new Alchemy({
  apiKey: process.env.ALCHEMY_API_KEY,
  network: Network.ETH_MAINNET,
});

async function getBalance(address: string) {
  const balanceWei = await alchemy.core.getBalance(address);
  const balanceEth = Utils.formatEther(balanceWei);
  console.log(`Balance of ${address}: ${balanceEth} ETH`);
  return balanceEth;
}

// Query Vitalik's address
getBalance('0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045').catch(console.error);

Step 2: Fetch NFTs for a Wallet

// src/hello-world/get-nfts.ts
import { Alchemy, Network } from 'alchemy-sdk';

const alchemy = new Alchemy({
  apiKey: process.env.ALCHEMY_API_KEY,
  network: Network.ETH_MAINNET,
});

async function getNftsForOwner(owner: string) {
  const nfts = await alchemy.nft.getNftsForOwner(owner);
  console.log(`Total NFTs: ${nfts.totalCount}`);

  for (const nft of nfts.ownedNfts.slice(0, 5)) {
    console.log(`  ${nft.contract.name} — ${nft.name || nft.tokenId}`);
    console.log(`    Contract: ${nft.contract.address}`);
    console.log(`    Token ID: ${nft.tokenId}`);
    if (nft.image?.cachedUrl) {
      console.log(`    Image: ${nft.image.cachedUrl}`);
    }
  }

  return nfts;
}

getNftsForOwner('vitalik.eth').catch(console.error);

Step 3: Get ERC-20 Token Balances

// src/hello-world/get-tokens.ts
import { Alchemy, Network } from 'alchemy-sdk';

const alchemy = new Alchemy({
  apiKey: process.env.ALCHEMY_API_KEY,
  network: Network.ETH_MAINNET,
});

async function getTokenBalances(address: string) {
  const balances = await alchemy.core.getTokenBalances(address);

  console.log(`Token balances for ${address}:`);
  for (const token of balances.tokenBalances.slice(0, 10)) {
    if (token.tokenBalance && token.tokenBalance !== '0x0') {
      // Get token metadata for human-readable names
      const metadata = await alchemy.core.getTokenMetadata(token.contractAddress);
      const balance = parseInt(token.tokenBalance, 16) / Math.pow(10, metadata.decimals || 18);
      console.log(`  ${metadata.symbol}: ${balance.toFixed(4)}`);
    }
  }
}

getTokenBalances('0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045').catch(console.error);

Step 4: Get Latest Block Info

// src/hello-world/get-block.ts
import { Alchemy, Network } from 'alchemy-sdk';

const alchemy = new Alchemy({
  apiKey: process.env.ALCHEMY_API_KEY,
  network: Network.ETH_MAINNET,
});

async function getLatestBlock() {
  const blockNumber = await alchemy.core.getBlockNumber();
  const block = await alchemy.core.getBlock(blockNumber);

  console.log(`Block #${blockNumber}`);
  console.log(`  Hash: ${block.hash}`);
  console.log(`  Timestamp: ${new Date(block.timestamp * 1000).toISOString()}`);
  console.log(`  Transactions: ${block.transactions.length}`);
  console.log(`  Gas Used: ${block.gasUsed.toString()}`);
}

getLatestBlock().catch(console.error);

Output

• ETH balance query with Wei → ETH conversion
• NFT enumeration with metadata and images
• ERC-20 token balances with symbol resolution
• Block data with timestamp and gas usage

Examples

Create a local .env entry through your secret-management workflow, run the balance and latest-block examples against a public address, and verify that the output contains only public chain data and no API key. Use a test address you control when adapting the NFT or token examples, and make one request at a time while learning the SDK. A successful run returns a block number or a well-formed empty asset list; it does not establish wallet ownership or asset value. If the address, network, or key is invalid, stop at the reported error, correct the configuration, and retry without copying the secret into source or terminal transcripts.

Error Handling

Resources

• Alchemy SDK Reference
• Alchemy NFT API
• Alchemy Enhanced APIs

Next Steps

Proceed to alchemy-local-dev-loop for development workflow setup.