[рони]

sendik,

function next() {
  index++;
  index = limit(index);
  show()
}
function prev() {
  index--;
  index = limit(index);
  show()
}

function setIndex(x) {
  index = x;
  index = limit(index);
  show();
}
function addIndex(x) {
  index += x;
  index = limit(index);
  show();
}

function limit(num) {
  if (num >= imgMassive.length) {
    num %= imgMassive.length ;
  }
if (num < 0) {
    num = imgMassive.length - (-num % imgMassive.length) ;
  }
  return num
}
function show()
{
   prev1.src = imgMassive[limit(index-2)];
   prev2.src = imgMassive[limit(index-1)];
   prev3.src = imgMassive[index];
   prev4.src = imgMassive[limit(index+1)];
   prev5.src = imgMassive[limit(index+2)];
   modal.style.display = 'block';
}