title: calling an onchange function from external javascript
body: <p>I have a select dropdown in a html file that i can't really touch</p>
  
  <pre><code>&lt;select id="color" onChange="javascript:changeColor(this)"&gt;
  &lt;option value="black"&gt;Black&lt;/option&gt;
  &lt;option value="red"&gt;Red&lt;/option&gt;
  &lt;option value="blue"&gt;Blue&lt;/option&gt;
  &lt;option value="gold"&gt;Gold&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>I am trying to manipulate that using prototype js </p>
  
  <pre><code>var update_dropdown=$$('select#color option');
  var option_length= update_dropdown.length;
  for (var m = 0; m &amp;lt; option_length; m++) {
      if(update_dropdown[m].value==selected_ColorId) {
          update_dropdown[m].selected=true;
      }
  }
  </code></pre>
  
  <p>is there any way that i can call onChange event that is being called in the html , like in this instance changeColor()?I am using prototype js
  thanks</p>