Map/Set to maintain unique array of arrays, Javascript

Question

I am trying to build unique array of arrays such that whenever I have new array to add it should only add if it doesn\'t already exist in collection

E.g. store all un

Answer 1

You can subclass Set for more flexibility in storing objects by storing the result of calling JSON.stringify on added objects.

class ObjectSet extends Set{
  add(elem){
    return super.add(typeof elem === 'object' ? JSON.stringify(elem) : elem);
  }
  has(elem){
    return super.has(typeof elem === 'object' ? JSON.stringify(elem) : elem);
  }
}
let set = new ObjectSet([[1,1,2],[1,2,1],[1,1,2],[1,2,1],[2,1,1],[2,1,1]]);
console.log([...set]);
console.log([...set].map(JSON.parse));//get objects back

Answer 2

If you are ok to use a library, try lodash uniqWith. This will recursively find groups of arrays OR objects with the comparator of your choice: equal in your case.

var arrayofarrays = [ [1,1,2], [1,2,1], [1,1,2], [1,2,1], [2,1,1], [2,1,1] ]

const uniqarray = _.uniqWith(arrayofarrays, _.isEqual);

console.log(uniqarray) //=> [[1, 1, 2], [1, 2, 1], [2, 1, 1]]

Bonus: it works on array of objects too

var objects = [{ 'x': 1, 'y': {b:1} }, { 'x': 1, 'y': {b:1} }, 
               { 'x': 2, 'y': {b:1} }, { 'x': 1, 'y': 2 }     ];

const uniqarray = _.uniqWith(objects, _.isEqual);

console.log(uniqarray) 
// => [{x: 1, y: {b: 1}}, {x: 2, y: {b: 1}}, {x: 1, y: 2}]

Answer 3

To get around the problem of each array being a unique object, you can stringify it so it's no longer unique, then map it back to an array later. This should do the trick:

var arr = [
  [1, 1, 2],
  [1, 2, 1],
  [1, 1, 2],
  [1, 2, 1],
  [2, 1, 1],
  [2, 1, 1]
];


var unique = arr.map(cur => JSON.stringify(cur))
  .filter(function(curr, index, self) {
    return self.indexOf(curr) == index;
  })
  .map(cur => JSON.parse(cur))

console.log(unique);

Answer 4

One way would be to convert the arrays to JSON strings, then use a Set to get unique values, and convert back again

var arr = [
  [1, 1, 2],
  [1, 2, 1],
  [1, 1, 2],
  [1, 2, 1],
  [2, 1, 1],
  [2, 1, 1]
];

let set  = new Set(arr.map(JSON.stringify));
let arr2 = Array.from(set).map(JSON.parse);

console.log(arr2)