dataTables添加序号和行选中框

<table id="mytable" class="table table-striped table-bordered" width="100%">
    <thead>
        <tr>
                <th>序号</th>
               <th>
                    <input type="checkbox" class="checkall" />
                </th> 
            </tr>
    </thead>
   <tbody></tbody>
</table>

$(document).ready(function(){
    var table = $("#mytable").DataTable({
            "processing":true,
             "ajax": {
                 "url": "user/getTableDatas",
             },
             "columns": [
                {"data":"index",//序号
           "render":function(data,type,row,meta){
            var startIndex = meta.settings._iDisplayStart;
            return startIndex+meta.row+1;
        }},
                {
                    "sClass": "text-center",
                    "data": "id",//行单选框
                    "render": function (data, type, full, meta) {
                      return '<input id="checkchild" type="checkbox"  class="checkchild"  value="' + data + '" />';
                    },
                    "bSortable": false
                }  
             ],
             //行被创建时调用
             "createdRow":function(row,data,dataIndex){
                 
             }
    });
    //复选框全选
    $(".checkall").click(function () {
          var check = $(this).prop("checked");
          $(".checkchild").prop("checked", check);
          checkButton();
    });
    //行内的选择框选中
    $(document).on("click","#checkchild",function(){
        var check = $(this).prop("checked");
        if(check && check==true){
            $(this).prop("checked",false);
        }else{
            $(this).prop("checked",true);
        }
        checkButton();
    });

    //选中行事件
    $("#mytable tbody").on("click","tr",function(){
        var check = $(this).find(".checkchild").prop("checked");
        if(check && check==true){
            $(this).find('.checkchild').prop("checked",false);
        }else{
            $(this).find('.checkchild').prop("checked",true);
        }
        checkButton();
      
    });