How to group by, calculate sum and get average in JavaScript array?

Question

I have array of object

 const users = [
     { group: \'editor\', name: \'Adam\', age: 23 },
     { group: \'admin\', n         


        

Answer 1

You could simply use reduce to get the total of age groups.

And use object.keys length to get the average of your total as new object from getAvg function.

Demo:

const users = [{
    group: 'editor',
    name: 'Adam',
    age: 23
  },
  {
    group: 'admin',
    name: 'John',
    age: 28
  },
  {
    group: 'editor',
    name: 'William',
    age: 34
  },
  {
    group: 'admin',
    name: 'Oliver',
    age: 28
  }
];

const sumId = users.reduce((a, {
  group,
  age
}) => (a[group] = (a[group] || 0) + age, a), {});

console.log(sumId); //{editor: 57, admin: 56}

//Average
const getAvg = (x) => {
  const item = {}
  const count = Object.keys(x).length
  Object.keys(x).map(function(y) {
    item[y] = sumId[y] / count
  })
  return item
}
console.log(getAvg(sumId)); //{editor: 28.5, admin: 28}