Duplicate value adding in array in Javascript

Question

I have a object like this :

totalProduct = [{name: "A", string: "Hello"}, {name: "A", string: "Hello"}, {name: "B", string: "Hey"}];

I calculate the total of the same name. So far everything is fine, I did this :

let counts = {};
for (const i in totalProduct) {
  const nameObject = totalProduct[i].name;
  const stringObject = totalProduct[i].string;

  counts[nameObject] = (counts[nameObject]||0) + 1;
}

The output is this :

{A:2, B:1}

BUT, i would like to have this output (Put the object value inside of an array with a string), but i don't know how to do this :(

{A:[2, 'Hello'], B:[1, 'Hey']}

I'have tried to do this but it's not working :

let counts = {};
for (const i in totalProduct) {
  const nameObject = totalProduct[i].name;
  const stringObject = totalProduct[i].string;

  counts[nameObject] = [(counts[nameObject]||0) + 1, stringObject];
}

The Hello and Hey come from const stringObject = totalProduct[i].string; — Rudy
– Rudy, Commented Feb 23, 2021 at 18:07
totalProduct = [{name: "A"}, {name: "A"}, {name: "B"}]; this does not have a property string — Damian
– Damian, Commented Feb 23, 2021 at 18:10
for every object with value A on its name property, they will also have the same string value? Could there be { name : 'A', string: 'Hello' } and { name : 'A', string: 'Hey' } ? — MinusFour
– MinusFour, Commented Feb 23, 2021 at 18:10

Maheer Ali · Accepted Answer · 2021-02-23 18:12:20Z

1

You need to set counts[nameObject] to an array of two elements

const totalProduct = [{name: "A", string: "Hello"}, {name: "A", string: "Hello"}, {name: "B", string: "Hey"}];

let counts = {};
for (const i in totalProduct) {
  const nameObject = totalProduct[i].name;
  const stringObject = totalProduct[i].string;
  const prevObj = counts[nameObject]
  counts[nameObject] = [(prevObj ? prevObj[0] : 0) + 1, stringObject];
}
console.log(counts);

answered Feb 23, 2021 at 18:12

Maheer Ali

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CertainPerformance · Accepted Answer · 2021-02-23 18:12:18Z

When iterating over the array, instead of putting just the count as the value in the object, put the [number, string] array (like your desired object) onto the object. On each iteration, create the array inside the object if the property doesn't exist yet, and then increment the [0]th item in the array regardless:

const arr = [{name: "A", string: 'Hello'}, {name: "A", string: 'Hello'}, {name: "B", string: 'Hey'}];

const obj = {};
for (const { name, string } of arr) {
  if (!obj[name]) obj[name] = [0, string];
  obj[name][0]++;
}
console.log(obj);

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