JQuery TablEdit add editable column dropdown option from database

I have a problem with TableEdit

This is in the documentation I read:

// Example #2
columns: {
    // Column used to identify table row.
    // [column_index, input_name]
    identifier: [0, 'id'],
    // Columns to transform in editable cells.
    // [[column_index, input_name], [column_index, input_name, select_options]]
    editable: [[1, 'car'], [2, 'color', '{"1": "Red", "2": "Green", "3": "Blue"}']]
}

In the editable key, the second array contains a json-like string that renders as a dropdown list when I press the edit button.

My question is, how do I make that json-like string dynamically?

I have an ajax request that returns a list of departments. I want to pass those departments into that editable column.