sum the values of a given array of objects sorted by a given property to sort on and the property containing the values to sum

combine-sets

/**
 * combine-sets
 * Created by dcorns on 5/16/17
 * Copyright © 2017 Dale Corns
 * MIT Licensed
 */
'use strict';
const data = [
  {
    "paid_savings": 8841.88,
    "queue_week": "201714",
  },
  {
    "paid_savings": 14021.05,
    "queue_week": "201714",
  },
  {
    "paid_savings": 17708.20,
    "queue_week": "201715",
  },
  {
    "paid_savings": 10270.08,
    "queue_week": "201715",
  },
  {
    "paid_savings": 4405.66,
    "queue_week": "201714",
  }
];
const combinedSums = (ary, combineKey, valueKey) => {
  let visited = [];
  let testIdx = 0;
  let result = [];
  ary.forEach((item) => {
    testIdx = visited.indexOf(item[combineKey]);
    if(testIdx < 0) {
      visited.push(item[combineKey]);
      result.push(item);
    }
    else{
      result[testIdx][valueKey] += item[valueKey];
    }
  });
  return new Promise ((resolve, reject) => {
    resolve (result);
  });

};
combinedSums(data, 'queue_week', 'paid_savings').then((res) => {
  console.log(res);
});