n this Kata, you will be given an array of numbers in which two numbers occur once and the rest occur only twice. Your task will be to return the sum of the numbers that occur only once. code example

Example: create a function that takes in an array of numbers and returns only the number that are even after 1 is added to the value

const evenAfter = (arr) => {
    let i = 0
    let newArr = []
    while (i <= arr.length) {
        if ((arr[i] + 1) % 2 === 0){          
            newArr.push(arr[i])
        }  
        i++
    }
    return newArr
}

console.log(evenAfter([3,6,7,8,9,11]))