javascript - Searching for a piece of code to update a textarea by selecting an <option> inside a <select> -

here code i've written few days ago. im relativels new php scene , not quite sure how can make working. want user can select his/her file appear inside textarea. created he/she can select file said already. cool helpers out there, can send me tip or whole anwser + code this? thank you, f9lke

<div class="bg-3 row">                   <div class="col-sm-4"></div>                     <div class="build_output">                     <div class="col-sm-4">                        <form action="viewer.php" method="post">                         <div class="bg-3-content">                           <div class="bg-3-hline">                             <h2>inhalt von <?php echo $selected; ?></h2>                           </div>                           <div class="bg-3-text">                             <p>hier sehen sie den inhalt der datei <?php echo $selected; ?> aus dem ordner <?php echo $ordner; ?>. <br> sie können diesen text bearbeiten und mit einem klick auf "speichern" die ursprungsdatei mit dem neuen text überschreiben.</p>                           </div>                         </div>                           <select name="dateien">                           <?php                           $ordner = "files";                           $alledateien = scandir($ordner);                           foreach ($alledateien $datei) {                             $dateiinfo = pathinfo($ordner."/".$datei);                               $size = ceil(filesize($ordner."/".$datei)/1024);                                if ($datei != "." && $datei != ".."  && $datei != "_notes") {                                $bildtypen = array("jpg", "jpeg", "gif", "png");                                if(in_array($dateiinfo['extension'], $bildtypen))                                { ?>                               <?php                                }else{                                   ?>                                 <option><?php echo $dateiinfo['filename']; ?> (<?php echo $dateiinfo['extension']; ?> | <?php echo $size ; ?>kb)</option>                                 <?php } ?>                                 <?php                                  };                              };                              ?>                            </select>                          <?php                           $selected = $_post['dateien'];                         ?>                          <textarea class="form-control" type="text" name="output" cols="60" rows="20">                             <?php                                $output = file_get_contents($dateiinfo['dirname']."/".$selected);                                echo $output;                                $latestcontent = $_post['output'];                              ?>                         </textarea>                          <br>                        <input class="output-save" type="submit" value="speichern" />                       <a href="#" class="output-abort">abbrechen</a>                        </form>                       </div>                     </div>                    <div class="col-sm-4"></div>               </div> <!--bg-3---> 

by using jquery can kinds of manipulations html.

jquery

// if select dropdown changes $(document).on('change', '.selector', function () {     // selected option     var option = $(this).val();     // if option optionone     if (option == 'optionone') {         // change textarea value         $('.textarea-selector').html('something');     } }); 

html

<select class="selector">     <option value="optionone">option one</option>     <option value="optiontwo">option two</option> </select>  <textarea class="textarea-selector">this change</textarea> 

i know simple example illustrate way solve problem nontheless.