如何从JavaScript循环中获取Select选项的值

I want to get / fetch value of select option from for-each loop in JavaScript

code

 <?php $user = $this->admin_model->getData('user'); ?>

 <select class="form-control" name="user" id="user">
        <option value="">Select User to Assign</option>
           <?php foreach ($user as $row): ?>
               <option value="<?php echo $row->id; ?>"><?php echo $row->user_name</option>
           <?php endforeach; ?>
 </select>

Try this.

<?php $user = $this->admin_model->getData('user'); ?>

 <select class="form-control" name="user" id="user" onchange="getValue(this)">
    <option value="">Select User to Assign</option>
       <?php foreach ($user as $row): ?>
           <option value="<?php echo $row->id; ?>"><?php echo $row->user_name;?></option>
       <?php endforeach; ?>
</select>

<script>
function getValue(sel){
   var optionvalue = sel.value;

    alert(optionvalue);

}
</script>

function myAlert(el){
  alert(el.options[el.selectedIndex].value);
}

 <select onchange="myAlert(this)" class="form-control" name="user" id="user">
            <option value="">Select User to Assign</option>
            <option value="value1">Value 1</option>
            <option value="value2">Value 2</option>
     </select>

</div>