Script to run on an exported Untappd JSON file that is open in Chrome to get your average brewery ratings.

averageBreweryRatings.js

Array.prototype.average = function () {
    var sum = 0, j = 0;
   for (var i = 0; i < this.length, isFinite(this[i]); i++) {
          sum += parseFloat(this[i]); ++j;
    }
   return j ? sum / j : 0;
};

var loadJSON = function() {
  return JSON.parse(document.getElementsByTagName("pre")[0].innerHTML);
}

var getAverages = function() {


  var checkins = loadJSON();
  var breweries = {};

  checkins.forEach(function (d) {
    var brewery = d.brewery_name;
    var rating = Number(d.rating_score);

    if (breweries[brewery]) {
      breweries[brewery].ratings.push(rating);
    } else {
      breweries[brewery] = {ratings: [rating]};
    }
  });

  for (var b in breweries) {
    var avg = breweries[b].ratings.average();
    breweries[b].average = avg;
    console.log(b + ": " + avg);
  }
}

getAverages();