如何使用CloudFunctionsforFirebase更新firebase实时数据库中的值

我通过firebase文档使用Cloud Functions for Firebase更新了实时数据库中的值,但我无法理解.

我的数据库结构是

{   
 "user" : {
    "-KdD1f0ecmVXHZ3H3abZ" : {
      "email" : "ksdsd@sdsd.com",
      "first_name" : "John",
      "last_name" : "Smith",
      "isVerified" : false
    },
    "-KdG4iHEYjInv7ljBhgG" : {
      "email" : "superttest@sds213123d.com",
      "first_name" : "Max1",
      "last_name" : "Rosse13131313l",
      "isVerified" : false
    },
    "-KdGAZ8Ws6weXWo0essF" : {
      "email" : "superttest@sds213123d.com",
      "first_name" : "Max1",
      "last_name" : "Rosse13131313l",
      "isVerified" : false
    } 
}

我想使用数据库触发器云功能更新isVerified.我不知道如何使用云函数更新数据库值(语言:Node.JS)

当使用数据库触发器onWrite创建用户时,我编写了一个代码来自动更新用户键'isVerified'的值.我的代码是

const functiOns= require('firebase-functions');

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

exports.userVerification = functions.database.ref('/users/{pushId}')
    .onWrite(event => {
    // Grab the current value of what was written to the Realtime Database.
    var eventSnapshot = event.data;

    if (event.data.previous.exists()) {
        return;
    }

    eventSnapshot.update({
        "isVerified": true
    });
});

TypeError: eventSnapshot.child(...).update is not a function
    at exports.userVerification.functions.database.ref.onWrite.event (/user_code/index.js:10:36)
    at /user_code/node_modules/firebase-functions/lib/cloud-functions.js:35:20
    at process._tickDomainCallback (internal/process/next_tick.js:129:7)

var eventSnapshot = event.data;
eventSnapshot.update({
    "isVerified": true
});

var ref = event.data.ref;
ref.update({
    "isVerified": true
});

return ref.update({
    "isVerified": true
});

var eventSnapshot = event.data;
eventSnapshot.update({
    "isVerified": true
});

var ref = event.data.ref;
ref.update({
    "isVerified": true
});

return ref.update({
    "isVerified": true
});