Detecting offset of an element on scroll in javascript / jQuery

I am looking to calculate the distance between an element and the top of the document window. On scroll I am able to get the initial value but it does not change. How can I find this value and what the number has changed to on scroll?

JS:

$(function() {
    $(window).scroll(function() {
        var h1 = $("h1");
        console.log(h1.offset().top)
    });
});

HTML:

<div id="cover">   
    <h1>hello sir</h1> 
</div>