JQuery append only accepts real JS arrays, not JQuery-objects representing arrays (as map returns). Solution: Convert to JS array with makeArray.

gistfile1.js

        $('<tr></tr>').append(
          $.makeArray($(data).map(function(index, element) {
            return $('<td></td>').html(element.instrument_name)
          }))
        ).appendTo(custom_factor_table) 
        $('<tr></tr>').append( 
          $.makeArray($(data).map(function(index, element) {
            return $('<td></td>').html('bla')
          }))
        ).appendTo(custom_factor_table)