jquery如何拿到dom元素的索引

 <script>
     
     $(document).on('mouseenter','.item',function() { 
     	let i = $(this).index();
     	console.log("元素的索引为：",i);
      	$('.header-out').css('display', 'block');
    });
     
      $(document).on('mouseleave','.item',function() {
      	$('.header-out').css('display', 'none');
    });
     
</script>