JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.6/css/bootstrap.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.2.4/jquery.min.js"></script>
<div id="my_dialog_template" >
    <div class="member_selection" id="dlg_member_selection" data-title="Member Selection">
        <div class="block_row">
            <label>&nbsp;</label>
            <label class="default_only">
                <input id="default_only" type="checkbox" />
                Default Member Only
            </label>
        </div>
        <div class="block_row">
            <label>Selected Member</label>
            <select class="selected_member" id="selected_member">
              <option>Val 1</option>
              <option>Val 2</option>
            </select>
        </div>
    </div>
</div>

JavaScript

$(function() {
	$('#default_only').on('change',function(){
     var isChecked = ($('#default_only:checked').val() == "on")? true : false;
     console.log(isChecked);
     $('#selected_member').prop('disabled', isChecked);
  });

});