mrluit / eth-scan

An efficient Ether and token balance scanner library

eth-scan

eth-scan is a library written in TypeScript, to help you fetch Ether or (ERC-20) token balances for multiple addresses in an efficient way. The library uses a smart contract to fetch the balances in a single call to a node. The contract is currently deployed at 0x82Ea2E7834Bb0D6224dd6fd7125d44b83d6D6809 on the Ethereum mainnet.

It can use Web3.js, Ethers.js or regular HTTP as provider to get the balances. See Getting Started for more info.

Note: Even though eth_call doesn't use any gas, the block gas limit still applies, and the maximum number of addresses you can fetch in a single call is limited. By default this library batches calls per 1000 addresses.

Getting started

The library is published on npm. To install it, use npm or yarn:

yarn add eth-scan

or

npm install eth-scan

Example

import EthScan, { HttpProvider } from 'eth-scan';

const scanner = new EthScan(new HttpProvider('http://127.0.0.1:8545'));

scanner.getEtherBalances([
  '0x9a0decaffb07fb500ff7e5d253b16892dbec006a',
  '0xeb65f72a2f5464157288ac15f1bb56c56e6be375',
  '0x1b96c634f9e9fcfb76932e165984901701352ffd',
  '0x740539b55ee5dc58efffb88fea44a9008f8daa6f',
  '0x95d9e32dc03770699a6a5e5858165b174d500015'
]).then(console.log);

Results in:

{
  '0x9a0decaffb07fb500ff7e5d253b16892dbec006a': 1000000000000000000n,
  '0xeb65f72a2f5464157288ac15f1bb56c56e6be375': 1000000000000000000n,
  '0x1b96c634f9e9fcfb76932e165984901701352ffd': 1000000000000000000n,
  '0x740539b55ee5dc58efffb88fea44a9008f8daa6f': 1000000000000000000n,
  '0x95d9e32dc03770699a6a5e5858165b174d500015': 1000000000000000000n
}

Note that this library uses the native JavaScript BigInt type, which currently does not work in all browsers. Use a polyfill if your application requires support for other browsers.

API

EthScan

new EthScan(provider, options?)

The main class used to get Ether or token balances.

• provider <Provider> - An instance of the Web3.js, Ethers.js or HTTP provider class.

• options <EthScanOptions> (optional) - The options to use.

getEtherBalances(addresses)

Get Ether balances for addresses.

• addresses <string[]> - An array of addresses as hexadecimal string.

• Returns: <Promise> - A promise with an object with the addresses and the balances.

getTokenBalances(token, addresses)

Get ERC-20 token balances from token for addresses. This does not check if the address specified is a token and will throw an error if it isn't.

• token <string> - The address of the ERC-20 token.

• addresses <string[]> - An array of addresses as hexadecimal string.

• Returns: <Promise> - A promise with an object with the addresses and the balances.

EthScanOptions

• contractAddress <string> (optional) - The address of the smart contract to use. Defaults to 0x82Ea2E7834Bb0D6224dd6fd7125d44b83d6D6809.

• batchSize <number> (optional) - The size of the call batches. Defaults to 1000.

Providers

There are currently three available providers.

new EthersProvider(provider)

Create a provider from an existing Ethers.js provider.

• provider <Provider> - An instance of an Ethers.js provider.

new HttpProvider(url)

Create a provider that uses a simple HTTP request.

• url <string> - The URL of the node to connect to.

new Web3Provider(web3)

Create a provider from an existing Web3.js instance.

• web3 <Web3> - An instance of the Web3 class.