how to prevent duplicates when using a javascript Map code example

Example 1: javascript remove duplicates from array

unique = [...new Set(arr)];   // where arr contains duplicate elements

Example 2: how to remove duplicates in array in javascript

const numbers = [1 , 21, 21, 34 ,12 ,34 ,12];
const removeRepeatNumbers = array => [... new Set(array)]
removeRepeatNumbers(numbers) // [ 1, 21, 34, 12 ]