title: How to handle unknown properties at design time in knockoutJS
body: <p>I am not sure, if I ask the question properly, so I try to explain the scenario. I have the feeling that I miss something simple in handling knockout.</p>
  
  <p>I read (and later write to) multiple xml files. These files have some entries that are equal and some entries that differs:</p>
  
  <pre><code>&lt;elements&gt;
    &lt;id&gt;123&lt;/id&gt;
    &lt;unknown&gt;some text&lt;/unknown&gt;
  &lt;/elements&gt;
  </code></pre>
  
  <p>After reading the xml files I come up with an observableArray which I can access as mentioned in most tutorials without any problem.</p>
  
  <p>So in this example I have no problem to read and edit the "id", cause I know that it calls "id":</p>
  
  <pre><code>&lt;span data-bind="text: $data.id"&gt;&lt;/span&gt;
  </code></pre>
  
  <p>But there are entries in the xml that i dont know, but they are in the observableArray and I can "see" that, if I refer to $data:</p>
  
  <pre><code>&lt;pre data-bind="text: ko.toJSON($data, null, 2)"&gt;&lt;/pre&gt;
  </code></pre>
  
  <p>This shows me the unknown parts:</p>
  
  <pre><code>...
  {
    "unknown": "some text"
  }
  ...   
  </code></pre>
  
  <p>To edit this property I had to access them by name or is there another option?
  So my problem is to access this for example via:</p>
  
  <pre><code>&lt;input data-bind="value: $data.???" /&gt;
  </code></pre>
  
  <p>If more information is required, please let me know.</p>
  
  <p>Thanks for ideas and answers.</p>