Count duplicates in an array of objects and sum up values located in the objects

Question

I have an array of objects that looks like this:

const users = [{name: 'John', gender: 'Male', orders: 20},
    {name: 'Doe', gender: 'Male', orders: 8},
    {name: 'Ada', gender: 'Female', orders: 10},
    {name: 'David', gender: 'Male', orders: 30}];

I need to count the number of duplicate genders and sum up the amount of orders based on gender located in the objects. I would like the final array to look like this:

[{gender: 'Male', count: 3, totalOrders: 58}, {gender: 'Female', count: 1, totalOrders: 10}]

This is the code I have so far:

const usersGender = users.map((user) => user.gender);

const result = Object.values(usersGender.reduce((a, b) => {
  a[b] = a[b] || [b, 0];
  a[b][1]++;
  return a;
},{})).map(item => ({gender: item[0], count : item[1]}));

console.log(result);

My output from the code above is:

[{ gender: 'Male', count: 3 }, { gender: 'Female', count: 1 }]

Thank you.

Nina Scholz · Accepted Answer · 2021-01-16 10:15:55Z

6

You could collect with an object and get the values from it.

const
    users = [{ name: 'John', gender: 'Male', orders: 20 }, { name: 'Doe', gender: 'Male', orders: 8 }, { name: 'Ada', gender: 'Female', orders: 10 }, { name: 'David', gender: 'Male', orders: 30 }],
    result = Object.values(users.reduce((r, { gender, orders }) => {
        r[gender] ??= { gender, count: 0, totalOrders: 0 };
        r[gender].count++;
        r[gender].totalOrders += orders;
        return r;
    }, {}));

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Jan 16, 2021 at 10:15

Nina Scholz

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