get the value of the href attribute onchange of dropdown

Question

I have a dropdown list where user can choose the different netweight. for example(200ml, 300ml etc).

      <?php 
      foreach($todays_offers as $offer)
      {
         $productname= $offer->product_name;
         $price= $offer->price;
         $brand= $offer->brand;
         $netweight= $offer->netweight;
         <div><?php echo $productname ?></div>
         <div><?php echo $price ?></div>
         <div><?php echo $brand ?></div>
       sql queries come here....
      <select name='netweight' id='netweight' onchange='ItemSelected(this)'>
        foreach ($query1->result() as $row) 
        {
            $net = $row->packing; 
            ?>
            <option id="<?php echo $row->id;?>" value="<?php echo $net;?>"><?php 
            echo $net;?>                            
           </option>
      </select> 
 <div class="product-button">
 <a class="add_cart" data-pname="<?php echo $productname ?>"  data-netweight="<?php echo $netweight?>"  data-price="<?php echo $price?>">
 add to cart</a></div>
}?>

my question is when the user choose the dropdownlist i want to set the 'data-netweight' attribute of a cart button to a selected drop down value. i have written the javascript code for onchange event and i am getting the selected value but i don know to set it to a datta-netweight attribute.

javascript

function ItemSelected(dropdown)
{

        var product_id = dropdown.options[dropdown.selectedIndex].id;
        var value = dropdown.options[dropdown.selectedIndex].value; 
        var linkitem = $('.product-button').find('a').data('netweight');

}

refer this image

Answer 1

Remove onchange from select

<?php 
      foreach($todays_offers as $offer)
      {
         $productname= $offer->product_name;
         $price= $offer->price;
         $brand= $offer->brand;
         $netweight= $offer->netweight;
         <div><?php echo $productname ?></div>
         <div><?php echo $price ?></div>
         <div><?php echo $brand ?></div>
       sql queries come here....
      <select name='netweight' id='netweight'>
        foreach ($query1->result() as $row) 
        {
            $net = $row->packing; 
            ?>
            <option id="<?php echo $row->id;?>" value="<?php echo $net;?>"><?php 
            echo $net;?>                            
           </option>
      </select> 
 <div class="product-button">
 <a class="add_cart" data-pname="<?php echo $productname ?>"  data-netweight="<?php echo $netweight?>"  data-price="<?php echo $price?>">
 add to cart</a></div>
}?>

Use id to get selected options

$(document).ready(function(){
     $("#netweight").change(function(){
        var optionsValue = $("#netweight option:selected").val();
        $(this).closest('a').attr('data-netweight',optionsValue);
     });
});

Answer 2

我用过parent（）

$(this).parent().find('a').attr('data-netweight',optionsValue);