Question

I want to reset childcombo box after disabled by parent combo. Child combo box is being disabled when i am selecting select option in parent combo box. After populating child combo box if i am selecting select option in parent combo, child combo is going to be disabled but how to reset child combo at this time that is child combo will also show please select option? What i need to add in javascript?

 <script type="text/javascript">
         $(document).ready(function() {
        $(function(){
var arrVal = ["RS", "MN", "KL"];
 $("#parentcombo").change(function(){
 var valToCheck = String($(this).val());

 if ( jQuery.inArray(valToCheck,arrVal) == -1 )
 {
 $("#childcombo").attr("disabled", "true"); 
 }
 else
{ 
         $("#childcombo").removeAttr ( "disabled" );    
}        
});
});
});     
    </script>

HTML

<select id="parentcombo">
<option value="_">select</option>
<option value="RS">RS</option>
<option value="MN">MN</option>
<option value="KL">KL</option>
</select>

<select id="childcombo" disabled="true">
<option value="_">please select</option>
<option value="somevalue">somevalue</option>
<option value="somevalue1">somevalue1</option>
<option value="somevalue2">somevalue2</option>
</select>

Answer 1

Use $('#childcombo').val("_") to select "please select" option in child combo box.

If you want to select any option in select element use val() method and pass the option value to it, it will select that option.

In your case since you want to select "please select" option in child combo box we used its value "_" to pass to val() method.

Alternative way using pure javascript is to set selectedIndex property of the select element.

$('#childcombo')[0].selectedIndex = 0;//option index to set selected