jQuery定位导航位置效果

当滚动条滚动到内容区域的时候，侧边导航条定位到屏幕，不再动，并且点击导航条跳转到内容所在的位置；
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <style>
        *{
            padding: 0;
            margin: 0;

        }
        .left{
            float: left;
            padding: 0 0 328px 0;
        }
        .left div{
            width: 800px;
            height: 300px;
            line-height: 300px;
            text-align: center;
            font-size: 30px;
            background: gray;
            margin: 10px 0;
        }
        .nav{
            position: absolute;
            right:20px;
            top: 20px;
        }
        .nav div{
            width: 100px;
            height: 80px;
            line-height: 80px;
            text-align: center;
            background: pink;
            margin: 10px 0;
            cursor: pointer;
        }
        .bottom{
            overflow: hidden;
            width: 100%;
            position: relative;
        }
    </style>
    <title>Document</title>
</head>
<body>
    <img style="100%" src="http://imagecdn.yinyuewujie.com/o_1bsmo1kpn1hp61bm0176i1bk618uo9.jpg" alt="">
    <div class="bottom">
        <div class="left">
            <div class="one leftDiv" id="one">
                一
            </div>
            <div class="conOne leftDiv" id="two">
                    二 
            </div>
            <div class="leftDiv" id="three ">
                三
            </div>
            <div class="leftDiv" id="four">
                四
            </div>
        </div>
        <div class="nav">
            <div class="one navDiv">one</div>
            <div class="two navDiv">two</div>
            <div class="three navDiv">three</div>
            <div class="four navDiv">four</div>
        </div>
    </div>
    <script src="jquery.js"></script>
    <script>
        $(window).scroll(function(e){
            console.log($(window).scrollTop());
            if ($(window).scrollTop() >$('#one').offset().top) {
               $('.nav').css({'position':'fixed'});
            console.log('ss');
            } else{
                $('.nav').css({'position':'absolute'});
            }
        })
        $('.nav div').click(function(){
            var i = $('.navDiv').index(this);
            var x = $('.leftDiv').eq(i).offset().top;
            $('html, body').animate({scrollTop:x+'px'},500);
        })
    </script>
</body>
</html>