@hemilabs/wallet-watch-asset

A JavaScript library for adding ERC20 tokens to EIP-747 compatible wallets like MetaMask. This package provides a simple way to help users track new tokens in their wallet.

Installation

npm install @hemilabs/wallet-watch-asset

Usage

The library provides a simple function to add an ERC20 token to a user's wallet watch list:

const watchAsset = require("@hemilabs/wallet-watch-asset");

// Example token (in Uniswap Token List format)
const token = {
  address: "0x1234567890123456789012345678901234567890",
  chainId: 1,
  decimals: 18,
  name: "My Token",
  symbol: "MTK",
  logoURI: "https://example.com/token-logo.png", // optional
};

// Using with MetaMask or other EIP-1193 provider
try {
  const success = await watchAsset(
    window.ethereum, // provider
    "0xUserAddress", // user's account
    token,
    localStorage, // optional, to track already-watched tokens
  );

  if (success) {
    console.log("Token added to watch list!");
  }
} catch (error) {
  console.error("Failed to add token:", error);
}

API

watchAsset(provider, account, token, storage?)

Helps EIP-747 compatible wallets track ERC20 assets.

Parameters

• provider (Provider): An EIP-1193 compatible provider (e.g., window.ethereum)

  • Must have a request method
  • isMetaMask property is checked to ensure compatibility

• account (string): The Ethereum address that will watch the token (must be in the format 0x...)

• token (Token): The token to watch (follows Uniswap Token List format)

  • address (string): The token contract address (must be in the format 0x...)
  • chainId (number): The chain ID where the token is deployed
  • decimals (number): The number of decimals for the token
  • name (string): The name of the token
  • symbol (string): The symbol for the token
  • logoURI (string, optional): A URI to the token logo asset

• storage (Storage, optional): Storage interface to track already-watched tokens (e.g., localStorage)

Returns

• Promise<true>: Resolves to true when the asset is successfully added to the watch list

Throws

• Throws an error if the wallet doesn't support EIP-747 or if the token addition fails