yahoo draft value scraper

scraper.js

// setup
// install if you don't have the below packages already
//
// $ npm install node-fetch --save
// $ npm install jsdom --save

// imports
const fs = require('fs');
const fetch = require('node-fetch');
const jsdom = require("jsdom");
const { JSDOM } = jsdom;

// config
const pages = [
  ['QB', 0],
  ['WR', 0],
  ['WR', 1],
  ['RB', 0],
  ['RB', 1],
  ['TE', 0],
];

const headers = [
  'Position',
  'Name',
  'Projected',
  'Average'
];

const outputFile = './yahoo_values.csv';

// utils
const baseUrl = 'https://football.fantasysports.yahoo.com/f1';
const staticSuffix = 'draftanalysis?tab=AD&sort=DA_AP';

const makeUrl = (position, page) => (
  `${baseUrl}/${staticSuffix}&pos=${position}&count=${page * 50}`
);

const toArray = (el) => Array.prototype.slice.call(el);

// parsing
const parseRowsFromDocument = (document) => {
  const rows = toArray(document.querySelectorAll('#draftanalysistable tbody tr'));

  return parsedDetails = rows.map(row => {
    const name = row.querySelector('.name').text;
    const valueElements = toArray(row.querySelectorAll('td')).slice(1, 3);
    const [projected, averageRaw] = valueElements.map(el => el.querySelector('div').innerHTML);
    const average = averageRaw === '$-' ? '$0' : averageRaw

    return [name, projected, average];
  });
}

const fetchCsvDataset = ([position, page]) => (
  fetch(makeUrl(position, page))
    .then(res => res.text())
    .then(body => {
      const dom = new JSDOM(body);
      const { document } = dom.window;

      const rows = parseRowsFromDocument(document);
      return rows.map(x => position + ',' + (x === '$-' ? '$0' : x).join(',')).join('\n');
    })
)

const main = () => Promise.all(pages.map(fetchCsvDataset))
  .then(datasets => {
    const csv = [headers, ...datasets].join('\n');

    fs.writeFile(outputFile, csv, (err) => {
      if (err) console.log('error!', err);
      console.log('success')
    })
  });

main();