table排名次

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title></title>
        <script type="text/javascript" src="js/jquery-2.1.4.min.js" ></script>
        <style>
            table{border-collapse: collapse; width: 100%; text-align: center;}
            table td{border: red solid 1px;}
        </style>
    </head>
    <body>
        <table class="mytb">
            <tr>
                <td>姓名</td>
                <td>分数</td>
                <td>排名</td>
            </tr>
            <tr >
                <td>小明</td>
                <td class="fs">108053</td>
                <td class="pm"></td>
            </tr>
            <tr>
                <td>小张</td>
                <td class="fs">180370</td>
                <td class="pm"></td>
            </tr>
            <tr>
                <td>小丁</td>
                <td class="fs">23002</td>
                <td class="pm"></td>
            </tr>
        </table>
        <p/>
        <table class="mytb">
            <tr>
                <td>姓名</td>
                <td>分数</td>
                <td>排名</td>
            </tr>
            <tr >
                <td>小明</td>
                <td class="fs">50</td>
                <td class="pm"></td>
            </tr>
            <tr>
                <td>小张</td>
                <td class="fs">100</td>
                <td class="pm"></td>
            </tr>
            <tr>
                <td>小丁</td>
                <td class="fs">90</td>
                <td class="pm"></td>
            </tr>
        </table>

        <script>
        function px(table){
            //把值推进数组
            var arr0=[];
            for(var i=1; i<$(table).find("tr").length; i++){
                arr0.push($(table).find("tr").eq(i). find(".fs").text());
            }

            //排序（此处不适合用冒泡）
            function sortNumber(a, b){return b - a}
            var arr=arr0.sort(sortNumber);

            console.log(arr);
            //赋值到排名
            for(var i=1; i<$(table).find("tr").length; i++){
                for (var z=0; z<arr.length; z++) {
                        if($(table).find("tr").eq(i). find(".fs").text()==arr[z]){
                            $(table).find("tr").eq(i). find(".pm").text(z+1)
                        }
                }
            }
        }

        for (var i=0; i<$(".mytb").length; i++) {
            px($(".mytb").eq(i))
        }
        </script>
    </body>
</html>