var current_card = cards.min; // start with the smallest card.
var straight = 0;
for(i=0;i==4;i++){
    if(cards[i] == current_card + 1){
        straight += 1;
        current_card = cards[i];
        i = -1; // resetting the loop.
        continue;
    }
    if(straight === 5)
        break;
}
if(straight === 5){
    // You have a straight.
}