Write a JavaScript program to find the maximal difference among all possible pairs of a given array of integers

function array_max_diff(arr) {

    var max_result = 0;

    for(var i=0;i<arr.length;i++)
       {
        for(var k=0; k!=i && k<arr.length; k++)
        {
            var diff = Math.abs(arr[i]-arr[k]);
            max_result = Math.max(max_result, diff);
        }
    }
    return max_result;
}
console.log(array_max_diff([1, 2, 3, 8, 9]))
console.log(array_max_diff([1, 2, 3, 18, 9]))
console.log(array_max_diff([13, 2, 3, 8, 9]))