Node.js script that downloads COVID cases for all countries (confirmed/deaths/recovered) and transforms it to tabular form.

corona-cases.js

const superagent = require("superagent");
const ExcelJS = require('exceljs');

const CORONA_API = 'https://coronavirus-tracker-api.herokuapp.com';

/**
 * @typedef {{
 *      id: number,
 *      name: string,
 *  }} Country
 * @typedef {{
 *      id: number,
 *      timelines: {
 *          confirmed: Object.<string, number>,
 *          deaths: Object.<string, number>,
 *          recovered: Object.<string, number>,
 *      }
 *  }} CountryTimeline
 */

/**
 * @typedef {{
 *      id: number,
 *      name: string,
 *  }} Country
 * @typedef {{
 *      id: number,
 *      timelines: {
 *          confirmed: Object.<string, number>,
 *          deaths: Object.<string, number>,
 *          recovered: Object.<string, number>,
 *      }
 *  }} CountryTimeline
 */

/**
 * @param {Country[]} countries
 * @param {CountryTimeline[]} countryTimelines
 * @returns {{
 *     confirmed: {columns: any[], rows: any[][]},
 *     deaths: {columns: any[], rows: any[][]},
 *     recovered: {columns: any[], rows: any[][]},
 * }} excel rows
 */
function transformTimelines(countries, countryTimelines) {
    const sheetColumnDates = {
        confirmed: new Set(),
        deaths: new Set(),
        recovered: new Set(),
    };
    const rows = {
        confirmed: [],
        deaths: [],
        recovered: [],
    }
    // columns
    countryTimelines.forEach(countryTimeline => {
        Object.keys(countryTimeline.timelines).forEach(timelineName => {
            Object.keys(countryTimeline.timelines[timelineName])
                .forEach(date => sheetColumnDates[timelineName].add(date));
        });
    });
    // rows
    countryTimelines.forEach(countryTimeline => {
        const countryName = countries.find(country => country.id === countryTimeline.id).name;
        Object.keys(countryTimeline.timelines).forEach(timelineName => {
            const timeline = countryTimeline.timelines[timelineName];
            if (Object.keys(timeline).length === 0 ) {
                return;
            }
            let dailyCases = [];
            const countryTimelineDates = new Set(Object.keys(timeline));
            const allTimelineDates = [...sheetColumnDates[timelineName]];
            allTimelineDates.forEach(timelineDate => {
                dailyCases.push(countryTimelineDates.has(timelineDate)? timeline[timelineDate]: null);
            });
            rows[timelineName].push([countryName, ...dailyCases]);
        });
    });

    /**
     * @param {Set.<string>} dates
     */
    function transformDatesToColumns(dates) {
        const datesSorted = [...dates].map(d => new Date(d));
        datesSorted.sort((d1,d2) => d1.getTime() - d2.getTime());
        return datesSorted.map(date => (
            {header: date, width: 15}
        ));
    }

    return {
        confirmed: {
            columns: [
                {header: "Country", width: 30},
                ...transformDatesToColumns(sheetColumnDates.confirmed),
            ],
            rows: [
                ...rows.confirmed,
            ]
        },
        deaths: {
            columns: [
                {header: "Country", width: 30},
                ...transformDatesToColumns(sheetColumnDates.deaths),
            ],
            rows: [
                ...rows.deaths
            ]
        },
        recovered: {
            columns: [
                {header: "Country", width: 30},
                ...transformDatesToColumns(sheetColumnDates.recovered),
            ],
            rows: [
                ...rows.recovered
            ]
        },
    };
}


/**
 * @returns {Promise<Country[]>}
 */
async function fetchCountries() {
    return superagent.get(`${CORONA_API}/v2/locations`)
        .then(res => res.body.locations.map(location => ({
            id: location.id,
            name: location.country + (location.province ? ` (${location.province})` : '')
        })));
}

/**
 * @param {number} countryId
 * @returns {Promise<CountryTimeline[]>}
 */
async function fetchCountryTimelines(countryId) {
    return superagent.get(`${CORONA_API}/v2/locations/${countryId}`)
        .then(res => ({
            id: res.body.location.id,
            timelines: {
                confirmed: res.body.location.timelines.confirmed.timeline,
                deaths: res.body.location.timelines.deaths.timeline,
                recovered: res.body.location.timelines.recovered.timeline,
            }
        }));
}

/**
 * @returns {Promise<{countries: Country[], countryTimelines: CountryTimeline[]}>}
 */
async function fetchTimelineData() {
    try {
        const countries = await fetchCountries();
        console.log('countries fetched');
        const countryIds = countries.map(country => country.id);
        const countryTimelines = await (Promise.all(
            countryIds.map(countryId => fetchCountryTimelines(countryId)))
        );
        console.log('country timelines fetched');
        return {
            countries: countries,
            countryTimelines: countryTimelines
        };
    } catch (e) {
        throw new Error(e);
    }
}

fetchTimelineData().then(timelineData => {
    const workbook = new ExcelJS.Workbook();
    const sheets = {
        confirmed: "Confirmed cases",
        deaths: "Death cases",
        recovered: "Recovery cases",
    };
    const excelData = transformTimelines(timelineData.countries, timelineData.countryTimelines);
    const options = {views: [{state: 'frozen', xSplit: 1, ySplit: 1}]};
    Object.keys(sheets).forEach(sheetName => {
        const worksheet = workbook.addWorksheet(sheets[sheetName], options);
        worksheet.columns = excelData[sheetName].columns;
        worksheet.addRows(excelData[sheetName].rows)
    });
    workbook.xlsx.writeFile("covid-cases.xlsx");
});