const img_max = 10;
let reader = new FileReader();
let files = [];  // user photos stored here
reader.onload = function (e) {
  $('#img_'+files.length).attr('src', e.target.result);
  $('#img_container_'+files.length).css('display', 'inline-block');
};

function readURL(input) {
  if (input.files && input.files[0]) {
    reader.readAsDataURL(input.files[0]);
    files.push(input.files[0]);
  }
}

$("#img_input").change(function() {
  if (files.length < img_max)
    readURL(this);
});

function deleteImg(index)
{
  let cur, next;
  for (let c = index; c < img_max; c++)
  {
    cur = $('#img_'+c);
    next = $('#img_'+(c+1)).attr('src');
    if (next == null) {
      cur.attr('src', null);
      $('#img_container_'+c).hide();
      break;
    }
    cur.attr('src', next);
  }
  files.splice(index, 1);
}

$('#form').submit(function (e)
    {
      let input = ($('#img_input'))[0];
      for (let c = 0; c < files.length; c++)
        input.files[c] = files[c];
      return true;
    });