javascript - Bigcartel Api get remaining items in Stock -

working on custom big cartel theme , done, part doesn't work when user updates number of products in cart, can set number value greater remaining stock. using big cartel api has variable called product var

 product.options-   returns of options of product whether   sold out or not. 

i loop through options 1 product so

  product.find(permalink, function(product) {   console.log("i found " + product.name + "!"); var len=(product.options.length); console.log(len);   for(var = 0; i<len;i++){       console.log((product.options[i]));    } }); 

the "option" object, according api has field

          option.quantity   returns quantity left in stock option. 

well when examine object loop prints

 object {id: 153343298, name: "small", price: 30, sold_out: false, has_custom_price: false} 

and there no "quantity" field. here link api documentation, have idea? big cartel api docs

found answer, default when click checkout button on bigcartel 'cart.html' page, element looks this

<form method="post" action="/cart"> <ul class="plain_list">    ... items in cart   </ul> <p class="subtotal">   ...  </p> <button type="submit" name="checkout" title="checkout">checkout</button> </form> 

it sumbits post request automatically checks if item quantity in cart greater remaining stock. element generates display error message looks has classes

<ul class="unstyled errors">        <!-- error message here-->                            </ul> 

i couldn't see because custom css blocked element.