js动态加载数据并合并单元格

js动态加载数据合并单元格，
代码如下所示，可复制直接运行：
<!DOCTYPE HTML>

<html lang="en-US">

<head>

    <meta charset="UTF-8">

    <title></title>

    <style>td{padding:2px 30px}</style>

</head>

<body>

<script type="text/javascript">

    var num =0;

    window.onload=function(){

    var myData=[

                    ["姓名","年龄","科目"],

                    ['张三','11',"语文"],

                    ['张三','11',"数学"],

                    ['张三','11',"数学"],

                    ['李四','11',"数学"],

                    ['李四','11',"数学"],

                    ['李四','11',"数学"],

                    ['www','11',"数学"],

                    ['www','11',"数学"],

                    ['www','11',"数学"],

                    ['www','11',"数学"]

               ]

    var str="<table border='1' cellspacing='0' cellpadding='0'><tbody>";

    var c=0;

    for(var i=0; i<myData.length; i++){

        if(i > 0) {

            if (myData[i][0] == myData[i - 1][0]) {

                str+="<tr><td>"+myData[i][1]+"</td><td>"+myData[i][2]+"</td></tr>";

            }else {

                 str+="</tbody>";

                  str+="<tbody>";

                  str+="<tr><td rowspan='1000'>"+myData[i][0]+"</td><td>"+myData[i][1]+"</td><td>"+myData[i][2]+"</td></tr>";

            }

        }else{

            str+="<tr><td>"+myData[i][0]+"</td><td>"+myData[i][1]+"</td><td>"+myData[i][2]+"</td></tr>";

        }

    }

    str+='</tbody></table>';

    //console.log(str);

    document.getElementById("table").innerHTML=str;

}

</script>

<div id="table" ></div>

</body>

</html>