Edit in JSFiddle

$(document).ready(function(){
  $('.cat').change(function(){
    var value = $(this).val();
    var load = $('#load').data('load');
    var lists = "";
    for(var cat in load){
      if(value === cat){
        load[cat].forEach(function(entry){
          lists += "<option>"+entry+"</option>";
        });
      }
    }
    $('.subcat').html(lists);
  });
});
<select class="cat">
  <option selected disabled>- Categories -</option>  
  <option>Bags</option>
  <option>Shoes</option>
  <option>T-Shirts</option>
</select>
  <br>
<select class="subcat">
  <option>- select a category -</option>
</select>
<div id="load" data-load='{"Bags":["Dolce & Gabanna", "Versace"],"Shoes":["Nike","Reebok","Adidas"],"T-Shirts":["Police", "Try"]}'></div>