growth_factor_calculator.js

const rp = require("request-promise");
const csv = require("csvtojson/v2");

const REPO_URL =
  "https://raw.githubusercontent.com/CSSEGISandData/COVID-19/master/csse_covid_19_data/csse_covid_19_time_series/time_series_covid19_confirmed_global.csv";

const limit = process.argv[2];
const offset = process.argv[3] || 0;

if (!limit || isNaN(limit) || limit < 1)
  return console.log(
    "Usage: npm run start [number limit] [optional number offset]"
  );

Array.prototype.cut = function(cutLength, cutOffset) {
  let result = this.splice(this.length - cutLength - cutOffset, Infinity);
  if (cutOffset) result = result.splice(0, cutLength);
  return result;
};

Number.prototype.divideBy = function(divisor) {
  return this / divisor;
};

rp(REPO_URL)
  .then((res) => csv().fromString(res))
  .then((jsonObj) =>
    Object.values(jsonObj.find((res) => res["Country/Region"] === "Argentina"))
      .splice(4)
      .map((_e, i, a) => (i ? a[i] - a[i - 1] : 0))
      .map((_e, i, a) => (i ? a[i] / a[i - 1] : 0))
      .cut(limit, offset)
      .reduce((a, c) => a + c, 0)
      .divideBy(limit)
  )
  .then(console.log)
  .catch(console.error);