You need to know how many pixels are rewound in a div block, counting from its bottom. If scrolling is squandered to the very end, should output 0.

I try to play with these parameters, but it does not:

var block = document.getElementById("mydiv"); alert (block.scrollTop + ' ' + block.scrollHeight);

    2 answers 2

    You can count it like this: block.scrollHeight - block.scrollTop - block.offsetHeight

     var block = document.getElementById("mydiv"); function calc() { alert (block.scrollHeight - block.scrollTop - block.offsetHeight + ' ' + block.scrollHeight); } 
     #mydiv { background: red; height: 150px; overflow-y: scroll; } .inner { height: 600px; } 
     <div id="mydiv"> <div class="inner"></div> </div> <button onclick="calc()">calc</button> 

       var block = document.getElementById("mydiv"); if (block.scrollHeight - block.scrollTop === block.clientHeight) { alert('Низ'); }