js push

    $('.main_div').each(function(){
        product_id = parseInt($(this).data('id'));
        product_num = parseInt($(this).data('num'));
        productList_array.productList.push({"productId":product_id,"quantity":product_num});
    });
    productList_array_jsonstr = JSON.stringify(productList_array);
    console.log(productList_array_jsonstr);