javascript array filter unique code example

Example 1: filter array with unique objects javascript

const array =
  [
    { "name": "Joe", "age": 17 },
    { "name": "Bob", "age": 17 },
    { "name": "Carl", "age": 35 }
  ]

const key = 'age';

const arrayUniqueByKey = [...new Map(array.map(item =>
  [item[key], item])).values()];

console.log(arrayUniqueByKey);

   /*OUTPUT
       [
        { "name": "Bob", "age": 17 },
        { "name": "Carl", "age": 35 }
       ]
   */

 // Note: this will pick the last duplicated item in the list.

Example 2: javascript array unique values

var arr = [55, 44, 65,1,2,3,3,34,5];
var unique = [...new Set(arr)]

//just  var unique = new Set(arr) wont be an array

Example 3: javascript find unique values in array

// usage example:
var myArray = ['a', 1, 'a', 2, '1'];
var unique = myArray.filter((v, i, a) => a.indexOf(v) === i); 

// unique is ['a', 1, 2, '1']

Example 4: array unique values javascript

const myArray = ['a', 1, 'a', 2, '1'];
const unique = [...new Set(myArray)]; // ['a', 1, 2, '1']

Example 5: javascript remove uniques from array

function getNotUnique(array) {
    var map = new Map();
    array.forEach(a => map.set(a, (map.get(a) || 0) + 1));
    return array.filter(a => map.get(a) > 1);
}

console.log(getNotUnique([1, 2, 2, 4, 4])); //[2, 2, 4, 4]
console.log(getNotUnique([1, 2, 3] )); //[]