how to clear an area of any duplicates in javascript code example

Example 1: javascript to remove duplicates from an array

uniqueArray = a.filter(function(item, pos) {
    return a.indexOf(item) == pos; 
})

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 ]