Firebase with Google Cloud Function -实时数据库验证，以检查尚未使用的用户名

firebase init functions

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

exports.checkUsername = functions.https.onCall(async (data, context) => {
  const username = data.username;

  // 检查用户名是否存在于实时数据库中
  const snapshot = await admin.database().ref(`users/${username}`).once('value');
  
  if (snapshot.exists()) {
    throw new functions.https.HttpsError('already-exists', 'Username already taken.');
  }

  return { exists: false };
});

firebase deploy --only functions

const firebase = require('firebase/app');
require('firebase/functions');

const functions = firebase.functions();

const checkUsername = functions.httpsCallable('checkUsername');

checkUsername({ username: 'desiredUsername' })
  .then(result => {
    console.log('Username is available:', result.data.exists);
  })
  .catch(error => {
    console.error('Error checking username:', error.message);
  });