javascript - data.map 函数在第二次调用后停止工作

Question

我有一个脚本，它每小时调用 API 并接收数据并自动将其存储在数据库中。该脚本本身在第一次调用时没有任何问题，但是当有时间第二次调用脚本时，它会给我一个错误。

示例：我在 13:30 开始脚本，在 14:00 脚本开始接收数据并将其存储在 MongoDB 中。第一次运行良好，但是当另一个时间到来时（在 15:00），脚本不想启动并且我收到此错误 -TypeError: data.map is not a function

我猜测问题出setTimeout在我添加之前的功能原因，一切都很完美。问题是我需要有 2 秒的延迟，否则我会收到来自 API 的 IP 禁令。

完整代码示例：

var requestPromise = require('request-promise');
const { MongoClient } = require('mongodb');
const schedule = require('node-schedule');
var XMLHttpRequest = require("xmlhttprequest").XMLHttpRequest;
const fetch = require("node-fetch");

var symbols = ["ZRXBTC",
    "LENDBTC",
    "AEBTC",
    "AIONBTC",
    "ALGOBTC",
    "ARDRBTC",

];
let cnt = 0;
const callIt = () => {
    fetch(`https://api.binance.com/api/v3/klines?symbol=${symbols[cnt]}&interval=30m&limit=1`)
        .then(res => res.json())
        .then(data => {
            const btcusdtdata = data.map(d => {
                return {
                    Open: parseFloat(d[1]),
                    High: parseFloat(d[2]),
                    Low: parseFloat(d[3]),
                    Close: parseFloat(d[4]),
                    Volume: parseFloat(d[5]),
                    Timespan: 30,
                }
            });
            console.log(btcusdtdata);
            saveToDatebase(btcusdtdata);
            cnt++;
            if (cnt < symbols.length) setTimeout(callIt, 3000);
        })
        .catch((err) => {
            console.log(err);
        })
};

const j = schedule.scheduleJob('*/0 * * * *', callIt)

const saveToDatebase = function(BTCdata) {

    const url = 'mongodb+srv://username:[e-mail]/<dbname>?retryWrites=true&w=majority';

    var today = new Date();
    var date = today.getFullYear() + '-' + (today.getMonth() + 1) + '-' + today.getDate();
    var time = today.getHours() + ":" + today.getMinutes() + ":" + today.getSeconds();
    var dateTime = date + ' ' + time;

    MongoClient.connect(url, { useNewUrlParser: true, useUnifiedTopology: true }, (err, db) => {
        if (err) throw err;
        const dbo = db.db('CryptoCurrencies');
        const myobj = { Name: symbols[cnt - 1], Array: BTCdata, Date: dateTime };
        dbo.collection(`${symbols[cnt - 1]}`).insertOne(myobj, (error, res) => {
            if (error) throw error;
            console.log('1 document inserted');
            db.close();
        });
    });

};

很快：该脚本每小时接收一次数据并将其存储在 MongoDB 中。我需要使用 setTimeout 从数组中延迟调用属性，否则我将收到来自 API 的 IP 禁令。该脚本在第一次工作时很好，但是当需要第二次调用时它给我一个错误 - TypeError: data.map is not a function。

只有在我添加setTimeout()功能后才会出现此问题。

标签： javascript

Answer 1

I think the problem is that the cnt variable is not reset to 0, returning undefined in the url on the second run (symbols[symbols.length] === undefined), returning a 404 from the fetch call, having no json body and thus dereferencing map on a non-array object.

Edit: The simple solution is to reset the counter to 0 once it has reached the end of the array.

const callIt = () => {
    fetch(`https://api.binance.com/api/v3/klines?symbol=${symbols[cnt]}&interval=30m&limit=1`)
        .then(res => res.json())
        .then(data => {
            const btcusdtdata = data.map(d => {
                return {
                    Open: parseFloat(d[1]),
                    High: parseFloat(d[2]),
                    Low: parseFloat(d[3]),
                    Close: parseFloat(d[4]),
                    Volume: parseFloat(d[5]),
                    Timespan: 30,
                }
            });
            console.log(btcusdtdata);
            saveToDatebase(btcusdtdata);
            cnt++;
            if (cnt < symbols.length) {
                setTimeout(callIt, 3000);
            } else {
                cnt = 0; // reset counter to 0 when cnt >= symbols.length to "prepare" for the next iteration initiated by schedule.scheduleJob
            }
        })
        .catch((err) => {
            console.log(err);
        })
};