(NodeJS)Google OAuth를 활용한 로그인 페이지 만들기

   <input type="button" class="button" value="">
    <script src="https://apis.google.com/js/platform.js" async defer></script>

 let gauth;
 const xhr = new XMLHttpRequest();
 let loginBtn = document.querySelector('.button');
 loginBtn.addEventListener('click', login); //이어서 설명

function login() {
  gapi.load('auth2', function () {
      gauth = gapi.auth2.init({
          client_id: 'Your Client id를 넣어주세요'
      });

      gauth.signIn().then(result => {
          let user = gauth.currentUser.get();
          let userName = user.getBasicProfile().getName();
          let userInfo_it = result.getAuthResponse().id_token;
          let userInfo_at = result.getAuthResponse(true).access_token;

          xhr.open('post', 'http://localhost:8080/auth/login', true);
          xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
          xhr.onreadystatechange = function () {
              if (xhr.readyState === xhr.DONE) {
                  if (xhr.status === 200 || xhr.status === 201) {
                      let payload = JSON.parse(xhr.responseText);
                      window.location.href = './next.html';
                      localStorage.setItem('token', payload.token);
                      localStorage.setItem('name', userName)
                  } else {
                      console.error(xhr.responseText);
                  }
              }
          };
          xhr.send("it=" + userInfo_it + "&at=" + userInfo_at);
      });
  });
}

const {
	OAuth2Client
} = require('google-auth-library');

const client = new OAuth2Client('구글 클라이언트 id');
const connection = require('../db/mysql');
const jwt = require('jsonwebtoken');

router.post('/login', (req, res, next) => {
	async function verify() {
		const ticket = await client.verifyIdToken({
			idToken: req.body.it
		});
		const payload = ticket.getPayload();
		const userid = payload['sub']; //21자리의 Google 회원 id 번호

		connection.execute('SELECT `TOKEN` FROM `innoboost_user` WHERE `ID`= ?', [userid], (err, results) => {
			if (err) throw err;
			let token = '';
			if (results.length > 0) {
				console.log('DB에 있는 유저', results);
				token = updateToken(payload);
			} else {
				console.log('DB에 없는 유저');
				//새로 유저를 만들면 jwt 토큰값을 받아온다.
				token = insertUserIntoDB(payload);
			}
			res.send({
				token
			});
		});
	}
	verify().then(() => {}).catch(console.error);
});

const updateToken = (payload) => {
	const {
		sub,
		name,
		email
	} = payload;
	console.log(`id: ${sub}\n name:${name}\n, email:${email}`);
	const token = jwt.sign({
			id: sub,
			name,
			email
		},
		JWT_SECRET
	);

	connection.execute('UPDATE `innoboost_user` SET `TOKEN`= ? WHERE (`ID`= ?)', [token, sub], (err, results) => {
		console.log(results)
	});
	return token;
}

const insertUserIntoDB = (payload) => {
	const {
		sub,
		name,
		email
	} = payload;
	console.log(`id: ${sub}\n name:${name}\n, email:${email}`);
	const token = jwt.sign({
			id: sub,
			name,
			email
		},
		JWT_SECRET
	);

	connection.execute(
		'INSERT INTO `innoboost_user` (ID, EMAIL, NAME, TOKEN) VALUES (?, ?, ?, ?)',
		[sub, email, name, token],
		(err, results, fields) => {
			if (err) {
				console.log('fail');
				throw err;
			}

		}
	);
	return token;
};