浏览器安装多个 web3 钱包，前端连接钱包指定用 MetaMask 的方式

先通过 ethereum?.providerMap 尝试找 MetaMask，如果找不到，返回默认的 ethereum

export default function getEthereum() {
  let ethereum = (window as any).ethereum?.providerMap?.get('MetaMask') || (window as any).ethereum?.providerMap?.get('metamask') || (window as any).ethereum?.providerMap?.get('Metamask')
  if (!ethereum) { 
    ethereum = (window as any).ethereum
  }
  return ethereum
}

使用方法：

const ethereum = getEthereum()