Implement shadow on the object from my predefine shadows in Sketch

I am not pro in javascript but I want to implement shadow on the object from my predefine shadows but the code is not working:

      var selection = context.selection;
      for (var i=0; i < selection.count(); i++){
        var layer = selection.objectAtIndex(i)

           if (layer.isEmpty) UI.message('No layers selected!');
           else {
                var sha_0 = [];
                var sha_1 = [
                color: '#00000024',
                 x: 0,
                 y: 1,
                 blur: 1,
                 spread: 0
                ]
                var sha_2 = [
                color: '#00036024',
                 x: 0,
                 y: 1,
                 blur: 1,
                 spread: 0
                ]
                var options = ['0dp', '1dp', '2dp'];
                var selectDialog = sketch.UI.getSelectionFromUser("Please select shadow depth:", options);
                if (selected == 0) {
                layer.forEach(function (e) {
                   e.style.shadows = sha_0;
                 });
               } else if (selected == 1) {
                 layer.forEach(function (e) {
                   e.style.shadows = sha_1;
                 });
               } else if (selected == 2) {
                 layer.forEach(function (e) {
                   e.style.shadows = sha_2;
                 });
               }
           }
      }

from Implement shadow on the object from my predefine shadows in Sketch