viem-erc20

Viem extensions for ERC20 tokens.

Installation

Install viem and viem-erc20 as dependencies:

npm install viem viem-erc20

Methods

This package provides ESM-friendly helpers for interacting with ERC20 contracts using viem.

allowance

Reads the allowance of a spender for a given owner.

allowance(client, { address, owner, spender });

• client: Client (from viem) — required
• address: Address — ERC20 contract address (required)
• owner: Address — Token holder address (required)
• spender: Address — Spender address (required)

Example:

import { allowance } from "viem-erc20/actions";
const result = await allowance(client, {
  address: "0x6B175474E89094C44Da98b954EedeAC495271d0F", // DAI
  owner: "0xYourWalletAddress",
  spender: "0xSpenderAddress",
});

balanceOf

Reads the balance of an account.

balanceOf(client, { account, address });

• client: Client (from viem) — required
• account: Address — Account to check balance for (required)
• address: Address — ERC20 contract address (required)

Example:

import { balanceOf } from "viem-erc20/actions";
const balance = await balanceOf(client, {
  account: "0xYourWalletAddress",
  address: "0x6B175474E89094C44Da98b954EedeAC495271d0F", // DAI
});

decimals

Reads the decimals value of an ERC20 token contract.

decimals(client, { address });

• client: Client (from viem) — required
• address: Address — ERC20 contract address (required)

Example:

import { decimals } from "viem-erc20/actions";
const tokenDecimals = await decimals(client, {
  address: "0x6B175474E89094C44Da98b954EedeAC495271d0F", // DAI
});

name

Reads the name value of an ERC20 token contract.

name(client, { address });

• client: Client (from viem) — required
• address: Address — ERC20 contract address (required)

Example:

import { name } from "viem-erc20/actions";
const tokenName = await name(client, {
  address: "0x6B175474E89094C44Da98b954EedeAC495271d0F", // DAI
});

symbol

Reads the symbol value of an ERC20 token contract.

symbol(client, { address });

• client: Client (from viem) — required
• address: Address — ERC20 contract address (required)

Example:

import { symbol } from "viem-erc20/actions";
const tokenSymbol = await symbol(client, {
  address: "0x6B175474E89094C44Da98b954EedeAC495271d0F", // DAI
});

totalSupply

Gets the total supply of the ERC20 token.

totalSupply(client, { address });

• client: Client (from viem) — required
• address: Address — ERC20 contract address (required)

Example:

import { totalSupply } from "viem-erc20/actions";
const tokenSupply = await totalSupply(client, {
  address: "0x6B175474E89094C44Da98b954EedeAC495271d0F", // DAI
});

approve

Sends an approval transaction to allow a spender to spend tokens on behalf of the owner.

approve(walletClient, { address, spender, amount });

• walletClient: WalletClient (from viem) — required
• address: Address — ERC20 contract address (required)
• spender: Address — Spender address (required)
• amount: bigint — Amount to approve (required, must be > 0)

Example:

import { approve } from "viem-erc20/actions";
const tx = await approve(walletClient, {
  address: "0x6B175474E89094C44Da98b954EedeAC495271d0F", // DAI
  spender: "0xSpenderAddress",
  amount: 1000000000000000000n, // 1 DAI (in wei)
});

Usage with .extend()

You can extend your viem client with ERC20 actions using .extend() and the provided helpers:

import { createPublicClient, createWalletClient, http } from "viem";
import { erc20PublicActions, erc20WalletActions } from "viem-erc20";

// Example: extending a public client
const publicClient = createPublicClient({
  chain, // your chain config
  transport: http(),
}).extend(erc20PublicActions());

// Now you can call:
const tokenAllowance = await publicClient.allowance({
  address: "0x6B175474E89094C44Da98b954EedeAC495271d0F",
  owner: "0xYourWalletAddress",
  spender: "0xSpenderAddress",
});

// Example: extending a wallet client
const walletClient = createWalletClient({
  account, // your account config
  chain, // your chain config
  transport: http(),
}).extend(erc20WalletActions());

// Now you can call:
const tx = await walletClient.approve({
  address: "0x6B175474E89094C44Da98b954EedeAC495271d0F",
  spender: "0xSpenderAddress",
  amount: 1000000000000000000n,
});

Local Setup

To install the dependencies, run:

npm install

To run the tests, run:

npm test