Remove Duplicates from an Array of GeoFire Objects

Question

I am working with Geofire and Firebase on Angular 6 to store locations and unfortunately it's storing a lot of duplicates this is an example (console logging my variable currentHits):

0: {location: Array(2), distance: "48.84", url: "assets/imgs/fix.png"}
1: {location: Array(2), distance: "48.84", url: "assets/imgs/fix.png"}
2: {location: Array(2), distance: "48.84", url: "assets/imgs/fix.png"}
3: {location: Array(2), distance: "48.85", url: "assets/imgs/free.png"}
4: {location: Array(2), distance: "48.85", url: "assets/imgs/free.png"}
5: {location: Array(2), distance: "48.85", url: "assets/imgs/free.png"}
6: {location: Array(2), distance: "48.87", url: "assets/imgs/low.png"}
7: {location: Array(2), distance: "48.87", url: "assets/imgs/low.png"}
8: {location: Array(2), distance: "48.87", url: "assets/imgs/low.png"}

Location basically is an array of latitude and longitude used to calculate distance, in id 0, 1 and 2 its the same coordinates, and 3,4 and 5 are also the same, ...

This is what I want to get:

0: {location: Array(2), distance: "48.84", url: "assets/imgs/fix.png"}
1: {location: Array(2), distance: "48.85", url: "assets/imgs/free.png"}
2: {location: Array(2), distance: "48.87", url: "assets/imgs/low.png"}

(Optional) this is how It stores these locations:

  ...
  hits = new BehaviorSubject([])

  ...
  queryHits(...){
 ....
 let hit = {
          location: location,
          distance: distance.toFixed(2),
          url:img
        }

        let currentHits = this.hits.value
        currentHits.push(hit)
        this.hits.next(currentHits)
....
}

It's true that this question has probably already been asked and I have been digging through all the similar questions and found these functions:

1. RemoveDuplicates()

function removeDuplicates(arr){
    let unique_array = []
    for(let i = 0;i < arr.length; i++){
        if(unique_array.indexOf(arr[i]) == -1){
            unique_array.push(arr[i])
        }
    }
    return unique_array
}

var newlist = removeDuplicates(list)

It didn't work I get the same list with duplicates.

2. arrUnique:

function arrUnique(arr) {
    var cleaned = [];
    arr.forEach(function(itm) {
        var unique = true;
        cleaned.forEach(function(itm2) {
            if (_.isEqual(itm, itm2)) unique = false;
        });
        if (unique)  cleaned.push(itm);
    });
    return cleaned;
}

var newlist= arrUnique(list);

Also, it didn't work..

3. onlyUnique

  onlyUnique(value, index, self) { 
    return self.indexOf(value) === index;
  }

var newlist = list.filter(onlyUnique)

Unfortunately it didn't work...

These are some of the answers given to similar problem to remove duplicates from an array and none of them worked. I don't understand why they won't work for my type of array, If anyone has an idea or knows why would be very helpful.

Answer 1

You could use a set to store and check for duplicate values.

const removeDuplicates = arr => {
    let matches = new Set();
    return arr.filter(elem => {
        const {distance} = elem;
        if(matches.has(distance)){
            return false;
        } else {
            matches.add(distance);
            return true;
        }
    })   
}

Bear in mind that using this approach you may remove results where the distance is the same but the co-ordinates differ. If that causes an issue for you then you'd need to also check against the lat/lng pair.