Having issue with Javascript

Here is my code: JS PART

$(document).ready(function(){
    $("#parent").hide();
    $(".parentcheck").click(function(){
            if($(this).val()==="1") 
            {
           开发者_StackOverflow中文版     $("#parent").show();
                $('#switch').attr('disabled', '');

            }
            else {
                $("#parent").hide();
                $('#switch').attr('disabled', 'disabled');
            }
    });

    $("#switch").change(function () {
    var selectedSwitch = $("#switch").val();
    var parentcheck = $(".parentcheck:checked").val();
    if (selectedSwitch!='' && selectedSwitch!='0'){
    $.ajax({
    type: "POST",
    url : "optionsgenerator.php",
    data: {menu: selectedSwitch},
    success: function(result, status, xResponse){
        if (result!=''){
            if($('#parentcheck').attr('checked')){
                $("#parent").hide();
            }
            else {
                $("#parent").html(result);
                $("#parent").show();
            }
        }
        else{
            alert('Error occured.');
            $("#parent").hide();
        }
    },
    error: function(e){
        alert(e);
    }
    });
    }
    else
    $("#parent").hide();
});

});

And HTML Markup

<select name="switch" id="switch">
<option value="" selected="selected">Select one...</option>
<option value="1">a</option>
<option value="2">b</option>
<option value="0">no one</option>
</select>

<div class="parent">
<input type="radio" class="parentcheck" name="parentcheck" value="0"/>
<input type="radio" class="parentcheck" name="parentcheck" value="1"/>

<select name="parent" id="parent"></select>
</div>

The problems is

If value of radio button with class "parentcheck" is 1, my js shows selectbox without checking if it has something to show (in my case options returned from backend php code) or not

I'm trying to achieve following

If value of radio button with class "parentcheck" is 1 then show selectbox #parent ONLY if ajax has already returned something, enable selectbox #switch

You are trying to get parentcheck by id, but parentcheck is a class:

var parentcheck = $("#parentcheck:checked").val();

try to change it to

var parentcheck = $(".parentcheck:checked").val();

EDIT: for the unselecting:

       if($(this).val()==="1") 
        {
            if ($("#parent option").length > 0) {
                 $("#parent").show();
            }
            $('#switch').attr('disabled', '');

        }
        else {
            $("#parent").hide().find('option:selected').removeAttr('selected');
            $('#switch').attr('disabled', 'disabled').find('option:selected').removeAttr('selected');
        }

Solutions:

1)

 if(selectedSwitch != '' && selectedSwitch !=0)

• you are shorting your OR statement, needs to be an AND.

2)

$(".parentcheck").click(function(){
        if($(this).val() == "1") 
        {
            $('#parent).show();
            $('#switch').attr('disabled', '');

        }
        else {
            $('#parent').val('');
            $('#parent').hide();
            $('#switch').val("Select one...");
            $('#switch').attr('disabled', 'disabled');
        }
});

• To set the value of the select, you need to give it the actual value of the index you want.

3) Set a boolean flag in your AJAX function, and then in the click listener only enable the selectbox if(flag).