combobox column type easy ui table

Question

in my table i have cloun combobox and datebox .

 

when i click that datebox does not give calendar and combobox does not list values . both are after entering some input then only it is work appropriately.

 

why  

 

<th data-options="field:'Subject',width:90" class="easyui-combobox" editor="{type:'combobox',options:

{

valueField:'id',

textField:'name',

data:[

{id:'computer',name:'Computer science'},

{id:'DS',name:'Data Structure'}

]}}">Subject</th>

 

<th data-options="field:'date',width:90"editor="{type:'datebox'}" formatter="format_date">Date of<br /