JS30-10.js

const inputs = Array.from(document.querySelectorAll('input'));
inputs.forEach(input => input.addEventListener('click', handleClick));

function clickBetween(first, last) {
  const direction = first < last ? 1 : -1;
  let index = first;
  while (index !== last) {
    index += direction;
    inputs[index].checked = true;
  }
}

let lastClicked = null;
function handleClick(e) {
  const clicked = e.currentTarget;
  if (clicked.checked) {
    if (e.shiftKey) {
      const clickedIndex = inputs.indexOf(clicked);
      const lastClickedIndex = inputs.indexOf(lastClicked)
      clickBetween(clickedIndex, lastClickedIndex);
    }
    lastClicked = clicked;
  }
}