remove all mutliple items from array javascript

arr = [2, 2, 2, 1, 3, 3, 3,3, 4, 5];
arr = arr.sort().filter((item,i)=>!(arr[i] == arr[i+1] || arr[i-1]==arr[i]));
// this will remove all item which are repeating more then one
console.log(arr);
// [1, 4, 5]

var arr1 = [1, 2, 3, 4, 5, 6];var arr2 = arr1; // Reference arr1 by another variable arr1 = [];console.log(arr2); // Output [1, 2, 3, 4, 5, 6]

var ar = [1, 2, 3, 4, 5, 6];ar.pop(); // returns 6console.log( ar ); // [1, 2, 3, 4, 5]