Put a class depending on the data ajax datatables

Question

I searched alot and I'm extremely sure it can be done easily but I cannot find a way to do it. So I use jQuery DataTables and I'm trying to generate a class and do a few javascript action depending on the value I'm recieving. For example, something as simple as putting a red background when the unit is negative, etc. I already created my CSS for this and now I'm loading a JSON file via the ajax parameters of DataTables. Here's my javascript:

     table = $('#activitiesTable').DataTable({
            "ajax": "data.txt",
            "columns": [
                { "data": "id" },
                { "data": "description" },
                { "data": "type_of_expenditure" },
                { "data": "real_cost" }
            ]
        });

I know that in the columns parameters, you can set a class right after by calling the "className" in the json, but I'm not sure how to generate a class by comparing a variable. For example, I'd like to do this:

      "columns": [
            {
               "data" : "id",
               "className": (data.id < 0 ? "negative" : "positive"))
            } 
       ]

Not sure if this can be done this way? Or if I have to check on jQuery everytime the ajax call is launched but I feel lt could be easily initialized right there...

Answer 1

I found that you can use it that way:

                 { 
                    "data": "forcast_profit_loss",
                    "createdCell": function (td, cellData, rowData, row, col) {
                      if ( cellData < 0 ) {
                        $(td).addClass('number number-negative');
                        $(td).text(cellData.substr(1));
                      }
                      else{
                        $(td).addClass('number number-positive');
                      }
                    }
                }

You can find references about it right there: https://datatables.net/reference/option/columns.createdCell