javascript - 如何在云函数的循环内设置await表达式？

Question

这是我的 firebase 云函数的简化代码:

const admin = require("../utilities/firebase_admin_init")
const db = admin.firestore()

exports.cronDeactivatingExpiredEvents = functions.https.onRequest(async (request,response) => {


    const now = new Date()
    const oneMonthAgo = moment().subtract(1,"month").toDate()


    try {
        const expiredEventsSnapshot = await eventRef
        .where("isActive","==",true)
        .where("hasBeenApproved","==",true)
        .where("dateTimeStart",">",oneMonthAgo)
        .where("dateTimeStart","<",now)
        .get()


        const expiredEventIDs = [] // list of IDs here ....


        // prepare promises to delete event data in user 'attendedEvents' subcollection.
        const deleteAttendedEventsDataPromises = []

        for (const eventID of expiredEventIDs) { 

            const eventAttendeeSnapshot = await db.collection("events").doc(eventID).collection("Attendee").get()
            const attendeeDocuments = eventAttendeeSnapshot.docs

            // getting all attendeeIDs.
            const attendeeIDs = []

            attendeeDocuments.forEach( attendeeSnapshot => {
                const attendee = attendeeSnapshot.data()
                attendeeIDs.push(attendee.uid)
            })

            attendeeIDs.forEach( attendeeID => {
                const p = db.collection("users").doc(attendeeID).collection("attendedEvents").doc(eventID).delete()
                deleteAttendedEventsDataPromises.push(p)
            })

        }

        // delete event data in user 'attendedEvents' subcollection
        await Promise.all(deleteAttendedEventsDataPromises)
        console.log(`successfully delete all events data in all attendee user subcollection`)


        response.status(200).send(`sucess`)

    } catch (error) {
        response.status(500).send(error)
    }



})

正如你在上面看到的，循环中有一个await表达式，但是我有一个如下图所示的错误标记，所以我无法部署该函数:

这是我运行firebase部署后出现的错误

/Users/muchammadagunglaksana/Documents/kumpul_muslim/cloud_functions_serverless_backend/functions/service/cron_operations.js 140:43 error Unexpected await inside a loop no-await-in-loop
170:41 error Unexpected await inside a loop no-await-in-loop

✖ 2 problems (2 errors, 0 warnings)

npm ERR! code ELIFECYCLE npm ERR! errno 1 npm ERR! functions@ lint: eslint . npm ERR! Exit status 1 npm ERR! npm ERR! Failed at the functions@ lint script. npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in: npm ERR!
/Users/muchammadagunglaksana/.npm/_logs/2019-12-14T10_47_36_788Z-debug.log

Error: functions predeploy error: Command terminated with non-zero exit code1

我尝试从这里阅读一些解决方案 Using async/await with a forEach loop 。就像这样使用for wait

确实，红色错误标记会消失，但我仍然无法部署该功能。这是我运行 firebase deploy

后出现的错误

functions[cronDeactivatingExpiredEvents(us-central1)]: Deployment error. Function failed on loading user code. Error message: Code in file index.js can't be loaded. Is there a syntax error in your code? Detailed stack trace: /srv/service/cron_operations.js:138 for await (const eventID of algoliaObjectIDs) { // algoliaObjectIDs is same as expired EventIDs ^^^^^

SyntaxError: Unexpected reserved word at createScript (vm.js:80:10) at Object.runInThisContext (vm.js:139:10) at Module._compile (module.js:617:28) at Object.Module._extensions..js (module.js:664:10) at Module.load (module.js:566:32) at tryModuleLoad (module.js:506:12) at Function.Module._load (module.js:498:3) at Module.require (module.js:597:17) at require (internal/module.js:11:18) at Object. (/srv/index.js:2:24)

在 .eslintrec.json 中我使用:

"parserOptions": {
    // Required for certain syntax usages
    "ecmaVersion": 2018
  },

我是云函数和后端开发的新手。如果我的问题太基本，我很抱歉。

我该怎么办？

Answer 1

第一个错误是关于eslint，有一条规则no-await-in-loop，它不允许在循环中等待，因为操作是串行的，而不是并行的基本上是为了减少资源和时间的浪费。

您可以做的就是像推送 Promises 一样使用它，然后执行 Promise.all ，或者您可以仅禁用该部分的规则。

/* eslint-disable no-await-in-loop */
for (const eventID of expiredEventIDs) { 

        const eventAttendeeSnapshot = await db.collection("events").doc(eventID).collection("Attendee").get()
        const attendeeDocuments = eventAttendeeSnapshot.docs
        ....
        ....
    }
/* eslint-enable no-await-in-loop */

第二个错误意味着您忘记将 for-await-of 包装在 async function 包装器中OR您正在使用 <强> Node 版本<10