Firebase v3事务和承诺

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

const firebaseConfig = {
  // Your Firebase config here
};

firebase.initializeApp(firebaseConfig);
const database = firebase.database();

function updateData(key, value) {
  const ref = database.ref(`data/${key}`);

  return ref.transaction(currentValue => {
    if (currentValue === null) {
      return value;
    } else {
      return currentValue + value;
    }
  });
}

updateData('counter', 1)
  .then(result => {
    console.log('Transaction completed:', result);
  })
  .catch(error => {
    console.error('Transaction failed:', error);
  });

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

const firebaseConfig = {
  // Your Firebase config here
};

firebase.initializeApp(firebaseConfig);
const database = firebase.database();

function getData(key) {
  const ref = database.ref(`data/${key}`);

  return ref.once('value')
    .then(snapshot => {
      return snapshot.val();
    });
}

getData('counter')
  .then(value => {
    console.log('Data retrieved:', value);
  })
  .catch(error => {
    console.error('Error retrieving data:', error);
  });

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

const firebaseConfig = {
  // Your Firebase config here
};

firebase.initializeApp(firebaseConfig);
const database = firebase.database();

function updateDataWithPromise(key, value) {
  const ref = database.ref(`data/${key}`);

  return ref.transaction(currentValue => {
    if (currentValue === null) {
      return value;
    } else {
      return currentValue + value;
    }
  }).then(result => {
    console.log('Transaction completed:', result);
    return result;
  });
}

updateDataWithPromise('counter', 1)
  .then(result => {
    console.log('Transaction result:', result);
  })
  .catch(error => {
    console.error('Transaction failed:', error);
  });