Select2 with multiple nested groups

Answer 1

I used like this. Working Fine.

$(document).on("ready", function() {
  function formatResult(node) {
    var level = 0;
    if(node.element !== undefined){
      level = (node.element.className);
      if(level.trim() !== ''){
        level = (parseInt(level.match(/\d+/)[0]));
      }
    }
    var $result = $('' + node.text + '');
    return $result;
  };

  $("#select2").select2({
    placeholder: 'Select an option',
    width: "300px",
    templateResult: formatResult,
  });
});