Sort grouped array in asc/desc order

Question

Can anyone assist in sorting the below array in ascending / descending order? The array is to be sorted based on the highest number in each grouping (grouped using brand). Numbers in each group are to be sorted as well:

original_array = [
  { brand: "Ford",   number: "1", },
  { brand: "BMW",    number: "1", },
  { brand: "BMW",    number: "5", },
  { brand: "BMW",    number: "20",},
  { brand: "Toyota", number: "10",}
];

desc_order = [
  { brand: "BMW",    number: "20",},
  { brand: "BMW",    number: "5", },
  { brand: "BMW",    number: "1", },
  { brand: "Toyota", number: "10",},
  { brand: "Ford",   number: "1", }
];

asc_order = [
  { brand: "Ford",   number: "1", },
  { brand: "Toyota", number: "10",},
  { brand: "BMW",    number: "1", },
  { brand: "BMW",    number: "5", },
  { brand: "BMW",    number: "20",}
];

Does this answer your question? [Sort array of objects by string property value](https://stackoverflow.com/questions/1129216/sort-array-of-objects-by-string-property-value) — Bahador Raghibizadeh, Oct 28 '21 at 15:21
The dupe reference is similar but does not deal with the max-requirement to drive the order of the first property. — trincot, Oct 28 '21 at 15:31

score 2 · Accepted Answer · answered Oct 28 '21 at 15:44

Since the order of the brands in the output depends on maximum values in their group, I would suggest to first create an object that lists the maximum number per brand.

Then use that to sort by, using the following sequence of ordering:

First by the maximum value for the brand
When that is equal, by the name of the brand (since several brands could have the same maximum number)
When that is equal, by the number itself

Implementation:

const array = [ { brand: "Ford", number: "1", }, { brand: "BMW", number: "1", }, { brand: "BMW", number: "5", }, { brand: "BMW", number: "20", }, { brand: "Toyota", number: "10", } ];

// First collect the maximum values per brand as an aggregate:
const aggr = {};
for (let {brand, number} of array) { 
    aggr[brand] = Math.max(number, aggr[brand] ?? number);
}

// Ascending
array.sort((a, b) => aggr[a.brand] - aggr[b.brand] 
                  || a.brand.localeCompare(b.brand)
                  || a.number - b.number);
console.log(array);

// Descending
array.sort((a, b) => aggr[b.brand] - aggr[a.brand]
                  || b.brand.localeCompare(a.brand)
                  || b.number - a.number);
console.log(array);

Sort grouped array in asc/desc order

1 Answers1