jQuery 数据表过滤具有特定类的行

let data = [{
  "item1": "this is item 1 - data set 1",
  "item2": "this is item 2 - meets condition1"
}, {
  "item1": "this is item 1 - data set 2",
  "item2": "this is item 2"
}, {
  "item1": "this is item 1 - data set 3",
  "item2": "this is item 2 - meets condition2"
}, {
  "item1": "this is item 1 - data set 4",
  "item2": "this is item 2 - meets condition1"
}, {
  "item1": "this is item 1 - data set 5",
  "item2": "this is item 2"
}, {
  "item1": "this is item 1 - data set 6",
  "item2": "this is item 2"
}, {
  "item1": "this is item 1 - data set 7",
  "item2": "this is item 2 - meets condition1"
}, {
  "item1": "this is item 1 - data set 8",
  "item2": "this is item 2 - meets condition2"
}, {
  "item1": "this is item 1 - data set 9",
  "item2": "this is item 2"
}];

var table = $('#table').DataTable({
  data: data,
  columns: [
    { "data": "item1",					  
     "render": function ( data, type, row ) {
       if(type === 'display'){
         return "<span class='format1'>"+data+"</span>";
       }else if(type === 'sort'){
         return data;
       }else if(type === 'filter'){
         return data;
       }else{
         return data;
       }
     }
    },
    { "data": "item2",					  
     "render": function ( data, type, row ) {
       if(type === 'display'){
         return "<span class='format2'>"+data+"</span>";
       }else if(type === 'sort'){
         return data;
       }else if(type === 'filter'){
         return data;
       }else{
         return data;
       }
     }
    }],
  createdRow: function ( row, data, index ) {
    if (data.item2 == 'this is item 2 - meets condition1'){
      $(row).addClass('condition1');
    }
    if (data.item2 == 'this is item 2 - meets condition2'){
      $(row).addClass('condition2');
    }
  }
});

$('#btn-filter').on('click',function(){
  $.fn.dataTable.ext.search.push(
    function(settings, data, dataIndex) {
      return $(table.row(dataIndex).node()).hasClass('condition1');
    }
  );
  table.draw();
});
$('#btn-undo').on('click',function(){
  $.fn.dataTable.ext.search.pop();
  table.draw();
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdn.datatables.net/1.10.13/js/jquery.dataTables.min.js"></script>
<link href="https://cdn.datatables.net/1.10.13/css/jquery.dataTables.min.css" rel="stylesheet"/>

<input type="button" id="btn-filter" value="click to select only condition1"/>
<input type="button" id="btn-undo" value="click to undo what '#btn-filter' did"/>
<br/><br/>

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