搜索、自动完成，支持ajax

官网：https://select2.github.io

支持嵌套结构###

<select>
  <optgroup label="Group Name">
    <option>Nested option</option>
  </optgroup>
</select>

初始化选择值，用于编辑###

      var changids = [];
      changIds = res.ids;
      savantSelect2.val(changIds).trigger('change'); //set the value  

事件监听###

$('select').on('select2:select', function (evt) {
  // Do something
});

获取选取##

    $('#select-user').on('select2:select', function (evt) {
        // Do something
        console.log($(this).find('option:selected').text());
    });

ajax remote 数据###

$('#barrier-sub-type').select2({
        ajax: {
            url: url,
            dataType: 'json',
            delay: 150,
            data: function (params) {
                return {
                    q: params.term // search term
                };
            },
            processResults: function (res) {
                // parse the results into the format expected by Select2.
                // since we are using custom formatting functions we do not need to
                // alter the remote JSON data
                return {
                    results: $.map(res.data, function (item) {
                        return {
                            text: item.name,
                            id: item.id
                        }
                    })
                };
            },
            cache: true
        },
    });