javascript生成表格

<script>
    function fnPrintTable(n,m){
        document.write("<table border=1 width=500>");
        for(var i = 1 ; i <= n ; i++){
            document.write("<tr>");
            for(var j = 1 ; j <= m ; j++){
                document.write("<td>"+Math.random()+"</td>");
            }
            document.write("</tr>");
            
        }
        document.write("</table>");
    }
    fnPrintTable(n,m);
</script>