title: ajax post selector as data in opencart "add to cart" button
body: <p>Recently I was learning opencart develop,I found a weird thing.
  We know the "add to cart" in product info page is using Ajax,and below the js code:</p>
  
  <pre><code>$('#button-cart').bind('click', function () {
      $.ajax({
          url: 'index.php?route=checkout/cart/add',
          type: 'post',
          data: $('.product-info input[type=\'text\'], .product-info input[type=\'hidden\'], .product-info input[type=\'radio\']:checked, .product-info input[type=\'checkbox\']:checked, .product-info select, .product-info textarea'),
          dataType: 'json',
          success: function (json) {
              /** code  **/
          });
      });
  </code></pre>
  
  <p>the post data is like a jQuery selector.why the post data isn't value? </p>