Sort a Map by a property of values while keeping the keys

Question

I have a map that’s declared like var cars = new Map<string, object>();, where the string is the model of the car and the object has information like year and price.

Therefore, the Map will look like this:

Map = [
        'BMW' => {
            id: 123,
            price: 2000,
            models: {...}
        },
        'Opel' => {
            id: 1234,
            price: 3500,
            models: {...}
        },
        ....
    ]

I would like to sort all the entires by the price field (asc, or desc).

I couldn’t figure out any solution, since iterating over the values would lose the keys, and solutions like I read around with ...cars.entries() doesn’t apply since the values are not iterable.

P.S. I am currently using TypeScript, but the solution for JS should apply nonetheless.

Edit: I tried converting the map to an array, like this:

const values = Array.from(this.cars.values());
values.sort((a, b) => {
    return (a.price < b.price) ? -1 : 1;
});

But I had some troubles reconstructing the Map to keep the keys…

Answer 1

A Map object iterates and keeps its elements in insertion order. So only solution for you to create new Map. Easiest way i think is to convert old map to array, sort it, and convert to a new map. Like this :

let newMap = new Map([...map].sort(([k, v], [k2, v2])=> {
  if (v.price > v2.price) {
    return 1;
  }
  if (v.price < v2.price) {
    return -1;
  }
  return 0; 
}));