Loop through object and add all values that are in a date range

I have a query that is getting values for the last 7 days for a user. These entries may be (2) or they may be (20) what's important is the values for each date are calculated and added.

here is the data:

[ { calories: '1170.00', upload_date: 2019-12-31T21:41:42.943Z },
  { calories: '2188.00', upload_date: 2019-12-31T21:41:56.604Z },
  { calories: '1079.00', upload_date: 2019-12-31T21:43:06.372Z },
  { calories: '2188.00', upload_date: 2019-12-31T21:42:56.577Z },
  { calories: '445.00', upload_date: 2019-12-31T21:42:45.559Z },
  { calories: '1170.00', upload_date: 2019-12-31T21:42:28.609Z },
  { calories: '445.00', upload_date: 2019-12-31T21:42:15.793Z },
  { calories: '1079.00', upload_date: 2019-12-31T21:42:05.049Z } ]

Now in this example the upload dates are the same, that's fine but what it should return is
{calories:sum of all, upload_date:"2019-12-31"} if there were seven days here I would need this to be a total of seven entries.

What I have tried:

I have tried several variations of using Date object and some array filtering but i did not arrive at a result I was content with and wanted to get a better way of doing it from here.

there needs to be a loop, a comparison of the date object(s) of all the keys in the objects and if they're equal add (+=) to the sum value of that particular day; then continue if there are more entries and repeat until all objects values have been added taking into respect the dates.

You can use a .reduce function to add each element of your array,

array.reduce((acc, el) => {}, {});

where el is an element of your original array.

Now with this accumulator you're using in .reduce, you can make the keys of this object be a date string that - importantly! - doesn't include the time. One way to do this is via new Date().toDateString(); which gives something like Fri Jan 03 2020

var reduced = array.reduce((acc, el) => {
    let newKey = new Date(el.upload_date).toDateString();
    if (acc[newKey]) {
        acc[newKey] += Number(el.calories);
    } else {
        acc[newKey] = Number(el.calories);
    }
    return acc;
}, {});

And now your 'reduced' object should look like {'Fri Jan 03 2020' : 300, 'Sat Jan 04 2020' : 324, }

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

const input = [ { calories: '1170.00', upload_date: '2019-12-31T21:41:42.943Z' },
  { calories: '2188.00', upload_date: '2019-12-31T21:41:56.604Z' },
  { calories: '1079.00', upload_date: '2019-12-31T21:43:06.372Z' },
  { calories: '2188.00', upload_date: '2019-12-31T21:42:56.577Z' },
  { calories: '445.00', upload_date: '2019-12-31T21:42:45.559Z' },
  { calories: '1170.00', upload_date: '2019-12-31T21:42:28.609Z' },
  { calories: '445.00', upload_date: '2019-12-31T21:42:15.793Z' },
  { calories: '1079.00', upload_date: '2019-12-31T21:42:05.049Z' },
  { calories: '1079.00', upload_date: '2019-12-30T21:42:05.049Z' } // added for demo
  ]
  
const output = input.reduce((all, next) => {
  const s = new Date(next.upload_date)
  const key = `${s.getFullYear()}-${(s.getUTCMonth() + 1)}-${s.getUTCDate()}`
  const exist = all.find(v => v.upload_date === key)
  if (exist) {
    exist.calories += Number(next.calories)
  } else {
    all.push({
      calories: Number(next.calories),
      upload_date: key
    })
  }
  
  return all
  
  
}, [])  

console.log(output)

<!-- end snippet -->

for(let i=7; i>=0; i--) {
   let day = new Date(Date.now() - (86400000 * i));
   let counts = data.filter(d => sameDay(day, d.upload_date));
   let caloriesOfThisDay = 0;
   counts.forEach(count => caloriesOfThisDay += count.calories);
   let dataOfThisDay = { colories: coloriesOfThisDay, upload_date: day };
}
function sameDay(d1, d2) {
    return d1.getFullYear() === d2.getFullYear() &&
      d1.getMonth() === d2.getMonth() &&
      d1.getDate() === d2.getDate();
}

First it calculates which day it is checking and then filter if its on desame day of the day it is checking.

After that, it checks all the calories and makes the data object you need.

If you want to sum by a specific date you could do something like this:

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

const test = [ { calories: '1170.00', upload_date: "2019-12-31T21:41:42.943Z" },
  { calories: '2188.00', upload_date: "2019-12-31T21:41:56.604Z" },
  { calories: '1079.00', upload_date: "2019-12-31T21:43:06.372Z" },
  { calories: '2188.00', upload_date: "2019-12-31T21:42:56.577Z" },
  { calories: '445.00', upload_date: "2019-12-31T21:42:45.559Z" },
  { calories: '1170.00', upload_date: "2019-12-31T21:42:28.609Z" },
  { calories: '445.00', upload_date: "2019-12-31T21:42:15.793Z" },
  { calories: '1079.00', upload_date: "2019-12-31T21:42:05.049Z" } ];

const filterDataByDate = (date) => test.filter(item => {
  const uploadDate = new Date(item.upload_date);
  const formattedUploadDate = uploadDate.getFullYear() + '-' + (uploadDate.getMonth() + 1) + '-' + uploadDate.getDate();
  //console.log(date,  formattedUploadDate, date === formattedUploadDate);
  return date === formattedUploadDate;
});

const sumOfCalories = filterDataByDate('2019-12-31').reduce((accumulator, currentValue) => {
  return accumulator += Number(currentValue.calories);
}, 0);

console.log("Sum of Calories:", sumOfCalories);

<!-- end snippet -->