var numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 100, 112, 113];

//remove all odd numbers,
//leaving only the even numbers
function removeOdds(numbers) {
    // remove all odd numbers from the input array (explicitly modify the contents of the parameter)
    removeOddsRecurse(numbers, 0)
}

function removeOddsRecurse(numbers, n) {
    if (n < numbers.length) {
        // have not exhausted the array
        var cur = numbers[n];
        if ((cur % 2) != 0) { // remainder, so remove it
            numbers.splice(n, 1);
        }
        else {
            n++;
        }
        removeOddsRecurse(numbers, n)
    }
}

console.log("before " + numbers);
//assert numbers.length == 13
removeOdds(numbers);
console.log("after " + numbers);
//assert numbers.length == 7