javascript how to get middle letters of a string
function extractMiddle(str) {
        var position;
        var length;
        if(str.length % 2 == 1) {
            position = str.length / 2;
            length = 1;
        } else {
            position = str.length / 2 - 1;
            length = 2;
        }
        return str.substring(position, position + length)
    }
    console.log(extractMiddle("handbananna"));