var range = [10, 20];
var not = [];

function randomRange(range, n) {
  if (not.length >= range[1] - range[0]) {
    not.length = 0;
  }
  var curr = [];
  var res = [];
  for (let i = range[0]; i < range[1]; i++) {
    if (!not.some(function(num) {
      return i == num
    }) && not.length < range[1] - range[0]) {
      curr.push(i)
    }
  }
  for (let i = 0; i < n; i++) {
    var j = curr.splice(Math.floor(Math.random() * curr.length), 1)[0];
    res[i] = not[not.length] = j;
  }

  return res.filter(Boolean)
}

function log(result) {
  document.body.innerHTML += JSON.stringify(result) + "<br>"
}

window.onload = function() {

log(randomRange(range, 3));
log(randomRange(range, 3));
log(randomRange(range, 3));
log(randomRange(range, 3));
log(randomRange(range, 3));
log(randomRange(range, 3));
log(randomRange(range, 3));
log(randomRange(range, 3));
log(randomRange(range, 3));
log(randomRange(range, 3));
}