@nomicfoundation/hardhat-verify/src/internal/chains.ts

Hardhat plugin for verifying contracts

import type { EthereumProvider } from "hardhat/types/providers";

const chainIdCache = new WeakMap<EthereumProvider, number>();

export async function getChainId(provider: EthereumProvider): Promise<number> {
  const cachedChainId = chainIdCache.get(provider);
  if (cachedChainId !== undefined) {
    return cachedChainId;
  }

  const chainId = Number(await provider.request({ method: "eth_chainId" }));
  chainIdCache.set(provider, chainId);

  return chainId;
}