check multiple checkboxes while shift key pressed

check_multiple.js

  const checkboxes = document.querySelectorAll('input[type="checkbox"]');
  checkboxes.forEach(c => c.addEventListener('click', handleCheck));

  let lastChecked = null;

  function handleCheck(e) {
    let inBetween = false;

    if(e.shiftKey && this !== lastChecked) {
      checkboxes.forEach(c => {
        const isEdge = c === this || c == lastChecked;
        if(isEdge) { inBetween = !inBetween }
        if(inBetween || isEdge) { c.checked = this.checked }
      })
    }


    lastChecked = this;
  }