Question

What I’m trying to do with javascript is:

Once you scroll so far down the page, change the position of #sidebar-box-fixed from position: relative; to position: fixed;. Change back to position: relative; once you scroll back up.

What would be the easiest way to do this?

Answer 1

You could try something in this direction:

$(document).ready(function() {
    var gap = 100;
    $(window).on('scroll', function(){
        var position = $(window).scrollTop() > gap ? 'fixed' : 'relative';
        $("#sidebar-box-fixed").css('position', position);
    });
});