Меняем Background через javascript

window.onload = function() { 
    function and do not restore data 
    if (sessionStorage.getItem('user') == " ") { 
      return; 
    } 
    if (sessionStorage.getItem('user') == " ") { 
      return; 
    } 
    var user = sessionStorage.getItem('user'); 
    if (user !== null) $('#user').val(user); 
    window.onbeforeunload = function() { 
      sessionStorage.setItem("user", $('#user').val()); 
    }

<select name="user" id="user" class="form-control"> 
   <option value="">Все</option> 
      <?php 
       while($test = mysqli_fetch_array($result)) { 
        $name = $test["userName"]; 
        echo '<option value="'.$name.'">'. $name .'</option>'; 
         } 
      ?> 
</select>