使用async/await时出现ReferenceError: updateSingle未定义问题求助

1. 直接修复 ReferenceError: updateSingle is not defined #

类内部调用自身方法必须使用this关键字，你在updateAll里直接写updateSingle，JS会认为这是全局函数，导致找不到定义。修改如下：

async updateAll(datesArr, apiManager) {
    // 先修正this的问题，后续再优化异步逻辑
    for (const date of datesArr) {
        await this.updateSingle(date, apiManager);
    }
}

2. 修复updateSingle中的异步遍历问题 #

forEach不支持异步等待，你在forEach里写的async id => {...}会生成一堆未被等待的Promise，导致updateSingle在所有API请求和数据库写入完成前就提前返回。推荐两种修复方案：

方案1：顺序执行（适合避免API请求并发过高） #

async updateSingle(day, apiManager) {
    for (const id of idList) {
        const reference = ref(this.db, `${day}/${id}`);
        const data = await apiManager.getDataApi(day, id, apiManager.season);
        await set(reference, data); // set是异步方法，必须加await
    }
}

方案2：并发执行（效率更高，注意API限流） #

async updateSingle(day, apiManager) {
    await Promise.all(idList.map(async id => {
        const reference = ref(this.db, `${day}/${id}`);
        const data = await apiManager.getDataApi(day, id, apiManager.season);
        return set(reference, data);
    }));
}

3. 优化updateAll的异步逻辑 #

同样，原forEach无法等待每个updateSingle完成，改成以下两种方式：

顺序执行 #

async updateAll(datesArr, apiManager) {
    for (const date of datesArr) {
        await this.updateSingle(date, apiManager);
    }
}

并发执行（最多10个节点，并发压力可控） #

async updateAll(datesArr, apiManager) {
    await Promise.all(datesArr.map(date => this.updateSingle(date, apiManager)));
}

4. 修复removeOldData的异步问题 #

当前removeOldData是同步方法，但onValue是异步回调，方法返回时foundOldDates还未被正确赋值，导致主程序里的dateRemoved永远为false。改成异步方法，用Promise包裹：

async removeOldData(datesArr) {
    const rootRef = ref(this.db, "/");
    return new Promise((resolve) => {
        let foundOldDates = false;
        onValue(rootRef, (snapshot) => {
            const deleteTasks = [];
            snapshot.forEach(dateSnap => {
                if (!datesArr.includes(dateSnap.key)) {
                    const oldDateRef = ref(this.db, `${dateSnap.key}/`);
                    deleteTasks.push(remove(oldDateRef));
                    foundOldDates = true;
                }
            });
            // 等待所有删除操作完成后返回结果
            Promise.all(deleteTasks).then(() => resolve(foundOldDates));
        }, { onlyOnce: true });
    });
}

主程序调用时需添加await：

dateRemoved = await firebaseManager.removeOldData(dateManager.dates);

完整修改后的代码 #

FirebaseManager类 #

import { initializeApp } from "firebase/app";
import { getDatabase, ref, remove, set, onValue } from "firebase/database";
import { ApiManager } from './api_manager.js';
import { idList } from '../data/data.js';
import { DateManager } from "./date_manager.js";

export class FirebaseManager {
    constructor() {
        this.firebaseConfig = {
            ...
        };
        this.app = initializeApp(this.firebaseConfig);
        this.db = getDatabase();
    }

    async updateSingle(day, apiManager) {
        await Promise.all(idList.map(async id => {
            const reference = ref(this.db, `${day}/${id}`);
            const data = await apiManager.getDataApi(day, id, apiManager.season);
            return set(reference, data);
        }));
    }

    async updateAll(datesArr, apiManager) {
        await Promise.all(datesArr.map(date => this.updateSingle(date, apiManager)));
    }

    async removeOldData(datesArr) {
        const rootRef = ref(this.db, "/");
        return new Promise((resolve) => {
            let foundOldDates = false;
            onValue(rootRef, (snapshot) => {
                const deleteTasks = [];
                snapshot.forEach(dateSnap => {
                    if (!datesArr.includes(dateSnap.key)) {
                        const oldDateRef = ref(this.db, `${dateSnap.key}/`);
                        deleteTasks.push(remove(oldDateRef));
                        foundOldDates = true;
                    }
                });
                Promise.all(deleteTasks).then(() => resolve(foundOldDates));
            }, { onlyOnce: true });
        });
    }
}

主程序 #

import { FirebaseManager } from "./firebase_manager.js";
import { ApiManager } from './api_manager.js';
import { DateManager } from './date_manager.js';

async function main() {
    let apiManager = new ApiManager();
    let dateManager = new DateManager();
    let firebaseManager = new FirebaseManager();

    await apiManager.getCurrentSeason();
    await firebaseManager.updateAll(dateManager.dates, apiManager);

    let countDaily = 0;
    let dateRemoved = false;

    while(true) {
        dateManager.update(); 
        if(countDaily >= 360) {
            await apiManager.getCurrentSeason();
            countDaily = 0; 
        }
        await firebaseManager.updateSingle(dateManager.getToday(), apiManager);
        dateRemoved = await firebaseManager.removeOldData(dateManager.dates);
        if(dateRemoved) {
            await firebaseManager.updateAll(dateManager.dates, apiManager);
            dateRemoved = false;
        }
        countDaily++;
        await new Promise(r => setTimeout(r, 240000)); 
    }
}

main();

内容的提问来源于stack exchange，提问作者bragi