how to find element which is not unique in array in javascript code example

Example 1: 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 2: array unique values javascript

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