函数返回未定义的、预期的 Promise 或值 [英] Function returned undefined, expected Promise or value

问题描述

当我在 firebase 上触发简单数据库触发器时，然后它将显示如下错误:函数返回未定义的、预期的 Promise 或值"

Whern i fire Simple database trigger on firebase, then it will shows Error like this : "Function returned undefined, expected Promise or value"

const firebase=require('firebase-admin');

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

exports.helloNotification = functions.database.ref('/users').onWrite(event => {

 return "A Notification has been deleted from the database ";
});

推荐答案

如果你在函数中没有任何异步工作要做，只需return null.返回字符串在 Cloud Functions 中没有任何意义.如果你出于某种原因需要返回一个 Promise，只需 return Promise.resolve().

If you don't have any asynchronous work to do in a function, just return null. Returning a string doesn't have any meaning in Cloud Functions. If you need to return a promise for some reason, just return Promise.resolve().

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