gistfile1.coffee

findCondenseOrCreate = (normalizedTag, name, fn) ->
  query = new Parse.Query("Category")
  query.equalTo "normalizedTag", normalizedTag

  query.find
    success: (results) ->
      [category, duplicates...] = results

      # We could try and collect numbers, but we really
      # don't care since we should be recounting anyway
      _.each duplicates, (duplicate) ->
        console.log "Destroying duplicate #{duplicate.get('normalizedTag')}"
        duplicate.destroy()

      if category
        fn(category)
      else
        category = new Parse.Object("Category")

        category.set
          normalizedTag: normalizedTag
          name: name

        fn(category)

    error: throwWithMessage

gistfile2.js

var findCondenseOrCreate,
  __slice = [].slice;

findCondenseOrCreate = function(normalizedTag, name, fn) {
  var query;
  query = new Parse.Query("Category");
  query.equalTo("normalizedTag", normalizedTag);
  return query.find({
    success: function(results) {
      var category, duplicates;
      category = results[0], duplicates = 2 <= results.length ? __slice.call(results, 1) : [];
      _.each(duplicates, function(duplicate) {
        console.log("Destroying duplicate " + (duplicate.get('normalizedTag')));
        return duplicate.destroy();
      });
      if (category) {
        return fn(category);
      } else {
        category = new Parse.Object("Category");
        category.set({
          normalizedTag: normalizedTag,
          name: name
        });
        return fn(category);
      }
    },
    error: throwWithMessage
  });
};