Firestore Cloud Function：出现“ReferenceError：firebase 未定义”

Question

I'm getting "ReferenceError: firebase is not defined" when running this firestore cloud function. I think the issue might be on the where clause but it looks defined since it's showing up on VSCode's IntelliSense.

const functions = require("firebase-functions");
const admin = require("firebase-admin");
var fetch = require("node-fetch");

admin.initializeApp();
const db = admin.firestore();

exports.sendPushNotifications = functions.firestore
  .document("/messages/{chatId}/chats/{messageId}")
  .onCreate(event => {
    let message = "";
    const members = event.get("members");
    const text = event.get("text");
    // const sender = event.get('user._id')
    return db
      .collection("users")
      .where(firebase.firestore.FieldPath.documentId(), "==", members[1])
      .get()
      .then(users => {
        users.docs.forEach(user => {
          var expoToken = user.data().notificationToken;
          if (expoToken) {
            message = {
              to: expoToken,
              body: text
            };
          }
        });
        return Promise.all(message);
      })
      .then(message => {
        return fetch("https://exp.host/--/api/v2/push/send", {
          method: "POST",
          headers: {
            host: "exp.host",
            accept: "application/json",
            "accept-encoding": "gzip, deflate",
            "content-type": "application/json"
          },
          body: JSON.stringify(message)
        });
      });
  });

Answer 1

Change this:

.where(firebase.firestore.FieldPath.documentId(), "==", members[1])

into this:

.where(admin.firestore.FieldPath.documentId(), "==", members[1])

For reference, check the following:

https://firebase.google.com/docs/reference/admin/node/admin.firestore