render function is called twice with type === 'display' for each cell

agoncharov

Hello DataTables team,

I've noticed strange behavior and can't find its reason. When I initialise a DataTable instance, which gets data via AJAX, like the following:

  settings_table = $('#settings_table').DataTable({
      paging: false,
      searching: false,
      info: false,
      order: [[1, 'asc']],
      columnDefs: [
        { orderable: false, targets: 0 },
      ],
      ajax: {
        url: '/settings.json'
      },
      columns: [
        { data: 'account' },
        { data: 'country' },
        { data: function (row, type, val, meta) {
          console.log(row);
          console.log(type);
          if(type === 'display') {
            return "test";  
          }
          return row;
        } }
      ]
    });

I see that function for third column (index 2) is called 3 times for every cell. First time it's called with type === 'display', second time — with type === 'type' and third time — with type === 'display'. I can't figure out, why it needs to execute the same function twice with 'display' type. Can you please explain?

I ask this because I want to generate HTML snippet for specific cells and want to avoid unnecessary processing. I use DataTables v.1.10.9

Could you please also advise, how to maximize rendering performance by caching cell's content. I tried to use columnDefs -> data: function for type === 'set', but didn't get it executed.

Thank you!