function that aggregates the win probabilities on fivethirtyeight's nba predictions page

get-predictions.js

function getPredictions(teamAbbreviation) {
  // run this at https://projects.fivethirtyeight.com/2021-nba-predictions/games/
  // teamAbbreviation can be one of the following:
  // 'DEN' 'PHX' 'LAC' 'UTA' 
  return new Promise((resolve) => {

    document.getElementById('js-upcoming-expander').click();
    const afterTimeout = () => {
      const selector = `#upcoming-days tr[data-team="${teamAbbreviation}"]`;
      const toFraction = (e) => Number(e.textContent.replace('%', '')) / 100;
      const chances = Array.from(document.querySelectorAll(`${selector} .chance`), toFraction);
      const teamName = document.querySelector(`${selector} .team`).textContent;
      const oppAbbreviation = document.querySelector(`#upcoming-days table.${teamAbbreviation}`).getAttribute('class').match(/[A-Z]{3}/g).filter(e => e !== teamAbbreviation)[0];
      const oppSelector = `#upcoming-days tr[data-team="${oppAbbreviation}"]`;
      const oppName = document.querySelector(`${oppSelector} .team`).textContent;
      const translator = s => {
        if (s.slice(0, 4) === '0000') {
          return `${oppName} in 4`;
        } else if (s.slice(0, 4) === '1111') {
          return `${teamName} in 4`;
        } else if (s.slice(0, 5).replace('1', '') === '0000') {
          return `${oppName} in 5`;
        } else if (s.slice(0, 5).replace('0', '') === '1111') {
          return `${teamName} in 5`;
        } else if (s.slice(0, 6).replaceAll('1', '') === '0000') {
          return `${oppName} in 6`;
        } else if (s.slice(0, 6).replaceAll('0', '') === '1111') {
          return `${teamName} in 6`;
        } else if (s.replaceAll('1', '') === '0000') {
          return `${oppName} in 7`;
        } else if (s.replaceAll('0', '') === '1111') {
          return `${teamName} in 7`;
        }
      };

      const allOutcomes = Array.from(new Array(128), (e, i) => {
        const s = i.toString(2).padStart(7, '0');
        return {
          probability: [...s].reduce((acc, e, i) => acc * (e === '0' ? 1 - chances[i] : chances[i]), 1),
          outcome: translator(s)
        };
      });

      const reducedOutcomes = allOutcomes.reduce((acc, e) => {
        if (e.outcome in acc) {
          acc[e.outcome] += e.probability;
        } else {
          acc[e.outcome] = e.probability;
        }

        return acc;
      }, {});

      resolve(reducedOutcomes);
    };

    setTimeout(afterTimeout, 1000);
  });
}