Ajax提交表单不起作用

Question

My submit button does not post the data to the $_POST. I have been browsing through the ajax form submission problems in this site, but none of the solutions posted work for my case.

JQUERY

$(document).ready(function(){
     $('form').on('submit', function(e){

          e.preventDefault();

          $.ajax({
            type: $(this).attr('method'),
            url:  $(this).attr('action'),
            data: $(this).serialize()

          });


    });
});

HTML

<form method="POST" action="add_item.php">


<div class="form-group">
    <label for="item_name">Item name </label>
    <input class="form-control" type="textfield" name="item_name" />
</div> 

<div class="form-group">
    <label for="quantity">Quantity</label>
    <input class="form-control quantity" type="textfield"     name="quantity"/> 
</div> 


<div class="form-group">
    <label for="capital">Capital</label>
     <input class="form-control capital" type"textfield" name="capital" /> 
</div> 

<div class="form-group">
    <label for="sellingprice">Selling Price</label>
   <input class="form-control sellingPrice" type="textfield" name="selling_price" /> 
</div> 

<div class="form-group">
    <button type="submit" class="btn btn-default">Submit</button>
</div>

</form>