Disabling a Dropdown list item jquery not working

I used each and it worked for me: https://jsfiddle.net/pz9curkb/1/

<select id="ChildOrganizationDropDownList">
    <option value="Default">Default</option>
    <option value="A">A</option>
    <option value="B">------- Internal -------</option>
    <option value="E">E</option>
</select>


 $("#ChildOrganizationDropDownList option").each(function(){   
     if($(this).text() === "------- Internal -------"){
        this.disabled  = true;
     }
});

Please note in this solution I used this instead of $(this), which means I used disabled option provided by javascript

First, ASP.NET might change the rendered client ID on your ChildOrganizationDropDownList control. In order to make this managable, you should set ClientIDMode to Static:

<asp:DropDownList ID="ChildOrganizationDropDownList" runat="server" Width="200px" ClientIDMode="Static" />

(See MSDN Library.) Now, you'll know that you can find this control using jQuery selector $("#ChildOrganizationDropDownList").

Secondly, I'm not sure that your JavaScript waits for the DOM to finish loading. If it fires too early, it will not find anything (since it's not loaded yet). Use $(document).ready(handler), or the shorthand $(handler).

Now, a JavaScript that disables all options with value "-1" in ChildOrganizationDropDownList could look like this:

$(function() { // Wait for the DOM to load
  $("#ChildOrganizationDropDownList option[value='-1']").attr("disabled", "disabled");
});

Try this:-

make sure you put the code in document.ready as below

$(document).ready(function(){
    $("select[ID$='ChildOrganizationDropDownList']").find("option").each(function(){   
         if($(this).text() === "------- Internal -------"){
            this.disabled  = true;
         }
    });    
});

Although I would advise you to rather provide support for 2 latest IE version rather than supporting IE8.

I tested the following code and it works fine.

    $(document).ready(function()
    {
        var valinp="------- Internal -------";
        $("#ChildOrganizationDropDownList option[value='" 
            +  valinp + "']").attr("disabled","");

    })

As you are supporting IE 8 you should include a jquery version which is < jQuery 2.x https://jquery.com/browser-support/

If you don't want the user to select that specific option why not hide it instead of disabling it?

$("#ChildOrganizationDropDownList option:contains('Internal')").hide();

Or even better remove it onclick of the object,

$(document).delegate("#ChildOrganizationDropDownList","click",function(){
    $(this).find("option:contains('Internal')").detach();
});

So they can't select it.

The following worked for me

$("#sel option[value=---Internal---]").prop('disabled','disabled');

Working JS Fiddle http://jsfiddle.net/jt47kj5n/1/

You can also try by wrapping the value with single quotes.

$("#sel option[value='---Internal---']").prop('disabled','disabled');

If the value -1 is never selectable accross your entire site then you can just do it very easily like this:

$('option[value=-1]').prop('disabled', true);

Otherwise you can do this:

1. Wrap your dropdown in div tags with an id (or you can also define a unique class and use it for all dropdowns with those properties):

   <div id="my-dropwdown">
       <asp:DropDownList ... />
   </div>
   

2. Select all the options inside the div with value="-1" and disable them:

   $('option[value=-1]', $('#my-dropdown')).prop('disabled', true);
   

   or

   $('option[value=-1]', $('#my-dropdown')).attr('disabled', 'disabled');
   

   and if you want to select over the class:

   $('option[value=-1]', $('.subContractingControls')).prop('disabled', true);
   

Actualy in ASP.net Webform architecture is also matter where you write your jQuery / javascript.

if you are adding script in your aspx page where control is place. you can use '<%= Control.ClientID %>' to get current if of control. If you are placing your code in aspx page but in header and your control is in your child page you can use

<%= Page.Master.FindControl("ContentPlaceHolder1").FindControl("Button1").ClientID %>'

  var currentControlID='<%= Control.ClientID %>';
    $("#"+currentControlID+" option").each(function(){   
     if($(this).text() === "------- Internal -------"){
        this.disabled  = true;
         }
    });

If you have separate js file then you have to set ClientIDMode="Static" for control and assign you id(but make sure this id must not be used for any other control and it must be unique in page.).