Please refer to the following code:
<select class="easyui-combogrid" style="width:250px" data-options="
panelWidth: 500,
idField: 'itemid',
textField: 'productname',
data: [
{itemid:'item1',productname:'name1'},
{itemid:'item2',productname:'name2'},
{itemid:'item3',productname:'name3'}
],
onLoadSuccess:function(data){
if (data.rows.length){
$(this).combogrid('setValue',data.rows[0].itemid);
}
},
columns: [[
{field:'itemid',title:'Item ID',width:80},
{field:'productname',title:'Product',width:120}
]],
fitColumns: true
">
</select>