该程序可将数据从T恤衫网站中抓取，然后将产品信息写入CSV文件。

有3个刮擦功能和1个写入功能。

现在，我陷入了一场绝对的噩梦，试图在没有任何第三方库或软件包的情况下实现如何在这里实现承诺。仅凭ES6的本机功能可以做到吗？

由于请求的异步性质，在调用下一个函数之前，我需要每个函数及其请求完全完成。这样，我就可以使用urlSet下一个函数中的变量。

我怎么能简单地做到这一点而无需重写我的整个代码？

我应该提到，这些功能中的每个功能都是单独工作的，它们都经过了多次测试。

每个功能是否都会成为一个单独的承诺？

代码如下，谢谢：

//TASK: Create a command line application that goes to an ecommerce site to get the latest prices.
    //Save the scraped data in a spreadsheet (CSV format).

'use strict';

//Modules being used:
var cheerio = require('cheerio');
var json2csv = require('json2csv');
var request = require('request');
var moment = require('moment');
var fs = require('fs');

//harcoded url
var url = 'http://shirts4mike.com/';

//url for tshirt pages
var urlSet = new Set();

var remainder;
var tshirtArray = [];


// First scrape loads front page of shirts4mike and finds the first product pages/menus
function firstScrape(){
    request(url, function(error, response, html) {
        if(!error && response.statusCode == 200){
            var $ = cheerio.load(html);

        //iterate over links with 'shirt'
            $('a[href*=shirt]').each(function(){
                var a = $(this).attr('href');

                //create new link
                var scrapeLink = url + a;

                //for each new link, go in and find out if there is a submit button. 
                //If there, add it to the set
                request(scrapeLink, function(error,response, html){
                    if(!error && response.statusCode == 200) {
                        var $ = cheerio.load(html);

                        //if page has a submit it must be a product page
                        if($('[type=submit]').length !== 0){

                            //add page to set
                            urlSet.add(scrapeLink);
                        } else if(remainder == undefined) {
                            //if not a product page, add it to remainder so it another scrape can be performed.
                            remainder = scrapeLink;                         
                        }
                    }
                });
            });     
        }
    });
}


//Scrape next level of menus to find remaning product pages to add to urlSet
function secondScrape() {
    request(remainder, function(error, response, html) {
        if(!error && response.statusCode == 200){
            var $ = cheerio.load(html);

            $('a[href*=shirt]').each(function(){
                var a = $(this).attr('href');

                //create new link
                var scrapeLink = url + a;

                request(scrapeLink, function(error,response, html){
                    if(!error && response.statusCode == 200){

                        var $ = cheerio.load(html);

                        //collect remaining product pages and add to set
                        if($('[type=submit]').length !== 0){
                            urlSet.add(scrapeLink);
                        }
                    }
                });
            });     
        }
    });
}


//call lastScraper so we can grab data from the set (product pages)
function lastScraper(){
    //scrape set, product pages
    for(var item of urlSet){
        var url = item;

        request(url, function(error, response, html){
            if(!error && response.statusCode == 200){
                var $ = cheerio.load(html);

                //grab data and store as variables
                var price = $('.price').text();
                var imgURL = $('.shirt-picture').find('img').attr('src');
                var title = $('body').find('.shirt-details > h1').text().slice(4);

                var tshirtObject = {};
                //add values into tshirt object
                tshirtObject.Title = title;
                tshirtObject.Price = price;
                tshirtObject.ImageURL = imgURL;
                tshirtObject.URL = url;
                tshirtObject.Date = moment().format('MMMM Do YYYY, h:mm:ss a');

                //add the object into the array of tshirts
                tshirtArray.push(tshirtObject);
            }
        });
    }
}


//Convert array of tshirt objects and write to CSV file
function convertJson2Csv(){
    //The scraper should generate a folder called `data` if it doesn’t exist.
    var dir ='./data';
    if(!fs.existsSync(dir)){
        fs.mkdirSync(dir);
    }

    var fields = ['Title', 'Price', 'ImageURL', 'URL', 'Date'];

    //convert tshirt data into CSV and pass in fields
    var csv = json2csv({ data: tshirtArray, fields: fields });

    //Name of file will be the date
    var fileDate = moment().format('MM-DD-YY');
    var fileName = dir + '/' + fileDate + '.csv';

    //Write file
    fs.writeFile(fileName, csv, {overwrite: true}, function(err) {
        console.log('file saved');
        if (err) throw err;
    });
}