Div scrollable from till

by Marian Rick

HTML

<div id="header">I am the hero</div>
<div id="wrapper">
    <div id="sidebar">
        <p>My skills:</p>
        <p>Scrollable at the beginning</p>
        <p>Fixed in the middle</p>
        <p>Scrollable at the end</p>
        <p id="exampleheight"></p>
    </div>
    <div id="content">Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi. Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi. Nam...

CSS

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    color: #fff;
    font-family: sans-serif;
}
#header {
    width: 100%;
    height: 100px;
    font-weight: bold;
    background: #5ec5c5;
    padding: 40px 50px 60px;
}
#wrapper {
    display: block;
}
#sidebar {
    float: left;
    width: 30%;
    background: #ffc34b;
    border-right: 20px solid #fff;
    padding: 20px;
}
.fixed #exampleheight {
    display: none;
}
p {
    margin-bottom: 10px;
}
#content {
    float: right;
    width: 70%;
    padding: 20px;
    background: #fbe2b7;
}
#footer {
    width: 100%;
    padding: 50px;
    background: #fd4f68;
}
#numbers {
    position: fixed;
    right: 0;
    width: 100px;
    background: #fff;
    border: 1px solid #000;
    z-index: 10;
    top: 0;
    color: #000;
    font-size: 0.5em;
    padding: 10px;
}
#numbers p {
    color: #000;
    margin-bottom: 0.4em;
}
#numbers p span {
    color: #000;
}
#numbers p:last-child {
    margin-bottom: 0;
}

JavaScript

$(document).ready(function () {

    // create vars for calculating
    var sidebar = $('#sidebar');
    var footer = $('#footer');

    var spacing_to_header = 80;
    var spacing_to_footer = 100;

    // do maths
    var window_height = $(window).height();
    var sidebar_height = sidebar.height();
    var sidebar_offset = sidebar.offset().top;
    var footer_offset = footer.offset().top;

    sidebar.css({
        "margin-top": spacing_to_header
    });

    $(window).scroll(function () {

        // create breakingpoints
        var scroll = $(window).scrollTop();
        // fixed start
        var scroll_fix_start = sidebar_offset + sidebar_height;
        // fixed end
        var scroll_fix_end = footer_offset - window_height + sidebar_height - spacing_to_footer;

        // make scrollable at the beginning
        if (scroll < scroll_fix_start) {
            sidebar.removeClass('fixed');
            sidebar.css({
                "position": "static",
                    "margin-top": spacing_to_header
            });
        }

        // fix scrollbar in the middle
        if (scroll > scroll_fix_start && scroll < scroll_fix_end) {
            sidebar.css({
                "position": "fixed",
                    "margin-top": 0,
                    "top": sidebar_offset
            });
        }

        // make it scrollable again
        if (scroll > scroll_fix_end) {
            sidebar.css({
                "position": "static",
                    "margin-top": scroll_fix_end
            });
        }

    });

    // Just for the demo
    $(window).scroll(function () {
        //You've scrolled this much:
        $('#scroll').text($(window).scrollTop() + " px");
    });
    $("#sidebar_height").append(sidebar_height);
    $("#sidebar_offset").append(sidebar_offset);
    $("#window").append(window_height);
    $("#footer_offset").append(footer_offset);
});