在coinbase-api回调函数中使用node.js for-loop索引

如何解决在coinbase-api回调函数中使用node.js for-loop索引

我是node.js的新手，我正在尝试制作一个简单的脚本，该脚本将连接到coinbase-api并获取MARKET数组中定义的任何市场的当前价格。

我遇到的问题是，遍历数组的for循环是异步的，并且回调函数没有为数组获取正确的索引值。

我发现的两个主要解决方案是使用Promise或强制循环等待。我认为我需要使用Promise，而不是强制for循环等待，但是老实说，我无法以任何一种方式实现解决方案。我已经找到了承诺的例子，但是我似乎无法弄清楚如何在我的脚本中实现它们。我将不胜感激。

const coinbaseModule = require('coinbase-pro');

const COINBASE_URI = 'https://api-public.sandbox.pro.coinbase.com';

// const MARKET = ['BTC-USD'];
const MARKET = ['BTC-USD','ETH-BTC'];

let askPrice = [null,null];

let averagePrice = [null,null];

let tickerCount = null;

const getCallback = (error,response,data) => 
{   
    if (error)
        return console.log(error);

    if ((data!=null) && (data.ask!=null) && (data.time!=null))
    {
        askPrice[tickerCount] = parseFloat(data.ask);
        
        if (averagePrice[tickerCount]===null)
        {
            averagePrice[tickerCount] = askPrice[tickerCount];
            console.log(MARKET[tickerCount] + " ask price: " + askPrice[tickerCount].toFixed(6));
        }
        else
        {   
            averagePrice[tickerCount] = (averagePrice[tickerCount] * 1000 + askPrice[tickerCount]) / 1001;
            console.log(MARKET[tickerCount] + " ask price: " + askPrice[tickerCount].toFixed(6) + " average price: "+ averagePrice[tickerCount].toFixed(6));
        }
    }
}

setInterval(() => 
{
    console.log('\n');
    publicClient = new coinbaseModule.PublicClient(COINBASE_URI); 

    for (tickerCount = 0; tickerCount < MARKET.length; tickerCount++) 
    {
        publicClient.getProductTicker(MARKET[tickerCount],getCallback);
    }

},10000);

解决方法

我能够从Mozilla开发人员网络上的有用示例中找出如何通过反复试验来使用诺言。我确定我会犯一些错误，但至少现在可以了。另一个小好处是我能够删除全局变量。

const coinbaseModule = require('coinbase-pro');

const COINBASE_URI = 'https://api-public.sandbox.pro.coinbase.com';

// const MARKET = ['BTC-USD'];
const MARKET = ['BTC-USD','ETH-BTC'];

let askPrice = [null,null];

let averagePrice = [null,null];

function getProductTicker(tickerCount) { 
  return new Promise(resolve => {
    publicClient.getProductTicker(MARKET[tickerCount],function callback(error,response,data){
        if (error)
            return console.log(error);

        if ((data!=null) && (data.ask!=null) && (data.time!=null))
        {
            askPrice[tickerCount] = parseFloat(data.ask);
            
            if (averagePrice[tickerCount]===null)
            {
                averagePrice[tickerCount] = askPrice[tickerCount];
                console.log(MARKET[tickerCount] + " ask price: " + askPrice[tickerCount].toFixed(6));
            }
            else
            {   
                averagePrice[tickerCount] = (averagePrice[tickerCount] * 1000 + askPrice[tickerCount]) / 1001;
                console.log(MARKET[tickerCount] + " ask price: " + askPrice[tickerCount].toFixed(6) + " average price: "+ averagePrice[tickerCount].toFixed(6));
            }
        resolve();
        }
    });
  });
}

setInterval( async () => 
{
    console.log('\n');
    publicClient = new coinbaseModule.PublicClient(COINBASE_URI); 

    for (var tickerCount = 0; tickerCount < MARKET.length; tickerCount++) 
    {
        await getProductTicker(tickerCount);
    }
},10000);