//打开下拉框

$('#id_select2_demo1').select2("open");

//获取下拉框中选中的数据

$("#id_select2_demo1").select2("data")

//清空下拉框中数据

$("#id_select2_demo1").select2("val", " ");

//赋值

$("#id_select2_demo1").val('1').trigger('change');  或者

$("#id_select2_demo1").val("1").select2();

<select class="form-control select2-hidden-accessible" id="id_select2_demo1" data-select2-id="id_select2_demo1" tabindex="-1" aria-hidden="true">

<div class="form-group" data-select2-id="10"><label class="control-label">Demo1 - 单选Demo：</label><select class="form-control select2-hidden-accessible" id="id_select2_demo1" data-select2-id="id_select2_demo1" tabindex="-1" aria-hidden="true"><option value="" data-select2-id="2">-----单选-----</option><optgroup label="Group-A" data-select2-id="14"><option value="1" data-select2-id="15">OPS-COFFEE-A</option><option value="2" data-select2-id="16">OPS-COFFEE-B</option></optgroup><optgroup label="Group-B" data-select2-id="17"><option value="3" data-select2-id="18">OPS-COFFEE-C</option><option value="4" data-select2-id="19">OPS-COFFEE-D</option></optgroup><optgroup label="Group-C" data-select2-id="20"><option value="5" data-select2-id="21">OPS-COFFEE-E</option><option value="6" data-select2-id="22">OPS-COFFEE-F</option></optgroup><option value="7" data-select2-id="23">OPS-COFFEE-G</option><option value="9" selected="" data-select2-id="94">我是新加的：ops-coffee.cn</option></select><span class="select2 select2-container select2-container--default select2-container--below" dir="ltr" data-select2-id="71" style="width: 1080px;"><span class="selection"><span class="select2-selection select2-selection--single" role="combobox" aria-haspopup="true" aria-expanded="false" tabindex="0" aria-labelledby="select2-id_select2_demo1-container"><span class="select2-selection__rendered" id="select2-id_select2_demo1-container" role="textbox" aria-readonly="true" title="我是新加的：ops-coffee.cn">我是新加的：ops-coffee.cn</span><span class="select2-selection__arrow" role="presentation"><b role="presentation"></b></span></span></span><span class="dropdown-wrapper" aria-hidden="true"></span></span></div>

https://www.520mwx.com/view/67866

demo:https://www.520mwx.com/view/67866