Why my if & else condition doesn't work correctly? [closed]

When I use this code to add & remove the style , Part ( else ) only works and sets (display) to block, But it will not return the class if clicked again. what's wrong?

var navDropDown = document.querySelectorAll('.menu-item-has-children > a');
for (let i = 0; i < navDropDown.length; i++) {
  navDropDown[i].addEventListener('click', (e) => {
    if (navDropDown[i].nextElementSibling.style.display = 'none') {
      this.nextElementSibling.style.display = 'block';
    } else {
      this.nextElementSibling.style.display = 'none';
    }
  })
}