云功能 - Cloud Firestore错误：无法获取serverTimestamp

Question

云功能 - Cloud Firestore错误：无法获取serverTimestamp

const admin = require('firebase-admin');
    exports.userlog = functions.firestore
    .document('user/{userId}')
    .onUpdate((change, context) => 
    { 
        const db = admin.firestore();
        //var timestamp = db.FieldValue.serverTimestamp();
        var timestamp = db.ServerValue.TIMESTAMP;
        ...
        return db.collection('userlog').add(
        {
            userId : previousValue.userId,
            ...
            timestamp: timestamp
        }).then(ref => 
        {
            return console.log('Added document with ID: ', ref.id);
        });
    });

我分别犯了两个错误：

  

TypeError：无法读取未定义的属性“serverTimestamp”

     

TypeError：无法读取未定义

的属性'TIMESTAMP'

Answer 1

正确的语法是：

firebase.firestore.FieldValue.serverTimestamp()

注意()之后缺少括号（firestore）：这是一个静态变量，而不是实例变量/成员字段。

Answer 2

// Imports: Dependencies
const admin = require('firebase-admin');

// Correct Syntax (If You Don't Want To Import Firestore)
created_at: admin.firestore.FieldValue.serverTimestamp(),