JavaScript's Math.random generate same numbers in the loop

I'm trying to generate different orders of taxi servise (I'll visualize them on Google Maps using Google Maps API). But I allways get only 2 versions of my route

while(index < documentNumber) {
    var random_number = Math.random();
    var randomIndex1 = Math.round(random_number * delta + INDEX_MIN);
    var randomIndex2 = Math.round(INDEX_MAX - random_number * delta);
    ...
}