Remove Duplicates from an Array of GeoFire Objects [duplicate]

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.

Answer 2

Problem here is comparing Objects. Two objects are never equal unless both are referencing to same Object.

Example:

{} === {} // false

// Two objects are equal only if they are referencing to same object
var a = {};
a === a; // true

It is clear from your problem that you are facing the first case. Among the solutions you tested Solution 1 and Solution 3 are failing because of this reason as indexOf does === comparision.

But Solution 2 should have worked on your example as it does a deep comparision as explained here. https://lodash.com/docs#isEqual.

PS: It might be a simple typo i have observed in Solution 2 cleaned.,push(itm);, there is an extra comma. Hoping that is not the case I am moving ahead

So i guess the issue is inside your location array, if you can give the contents of location array we should be able to provide better solution. Or as others suggested you can filter based on a single key of the object like id or distance, instead of comparing the whole object