shift select logic for checkboxes

shift-select-checkboxes.js

const checkboxes = document.querySelectorAll('.checkbox input[type="checkbox"]');
let lastChecked;

function handleCheck(e) {
  let inBetween = false;

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

      if(inBetween) {
        checkbox.checked = true;
      }
    });
  }
  lastChecked = this;
};

checkboxes.forEach(checkbox => checkbox.addEventListener('click', handleCheck));