有人可以规范地区分scrollTop和scrollHeight吗？

For example,

例如，

function fnCheckScroll(){   
    var iNewHeight = oDiv.scrollHeight;
    var iscrolTop = oDiv.scrollTop; 
    alert("The value of the scrollHeight property is: "  + iNewHeight + "px"); 
    alert("The value of the scrollTop property is: " + iscrolTop + "px");        
}

<div id="oDiv" style="overflow: scroll; height= 100px; width= 250px; text-align: left">
Hello<br>
</div>
function fnCheckScroll(){