Firebase:如何取回数组而不是对象

// 存储数据
const data = {
  0: "item1",
  1: "item2",
  2: "item3"
};

firebase.database().ref('path/to/data').set(data);

// 取回数据
firebase.database().ref('path/to/data').once('value').then(snapshot => {
  const data = snapshot.val();
  const array = Object.keys(data).map(key => data[key]);
  console.log(array); // ["item1", "item2", "item3"]
});

// 存储数据
const data = {
  items: ["item1", "item2", "item3"]
};

firebase.database().ref('path/to/data').set(data);

// 取回数据
firebase.database().ref('path/to/data').once('value').then(snapshot => {
  const data = snapshot.val();
  const array = data.items;
  console.log(array); // ["item1", "item2", "item3"]
});

// 存储数据
const data = ["item1", "item2", "item3"];

firebase.firestore().collection('collectionName').doc('documentId').set({ items: data });

// 取回数据
firebase.firestore().collection('collectionName').doc('documentId').get().then(doc => {
  if (doc.exists) {
    const data = doc.data();
    const array = data.items;
    console.log(array); // ["item1", "item2", "item3"]
  } else {
    console.log("No such document!");
  }
});