How to use a metamask in browser.

메타마스크가 설치된 browser에서는 metamask가 자동으로 window.ethereum을 주입해주고 메타마스크와 관련된 모든 api는 window.etheurem을 통해 호출할수 있다.

how to detect metamask

if (typeof window.ethereum === 'undefined') {
  alert('Looks like you need a Dapp browser to get started.')
  alert('Consider installing MetaMask!')

} else {
  // can use a metamask
}

logging in

window.ethereum.enable()를 통해 metamask의 accounts 정보를 가져 올 수 있다. 기본적으로 mainnet의 계정을 가져오고 ethereum.selectedAddress 값 설정을 통해 원하는 블록체인 네트워크의 계정을 가져올 수 있다.

const accounts = await window.ethereum.enable()
const account = accounts[0]

Execute transaction

window.ethereum.sendAsync()를 통해 transaction을 발생시킬 수 있다. from에 account 정보를 넣어준다.

const method = 'eth_sendTransaction'
const parameters = [{
    from: account,
    to: yourAddress,
    value: value,
}]
const from = account

// Now putting it all together into an RPC request:
const payload = {
    method: method,
    params: parameters,
    from: from,
}

// Methods that require user authorization like this one will prompt a user interaction.
// Other methods (like reading from the blockchain) may not.
ethereum.sendAsync(payload, function (err, response){
 ...
}

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