title: KnockoutJS Object doesn't support 'toFixed'
body: <p>I'm using KnockoutJS and am running into an issue that I have no idea how to go about finding a solution to:</p>
  
  <p>I have a table containing records:</p>
  
  <pre><code>&lt;script type="text/html" id="myItemsTemplate"&gt;
  &lt;tr&gt;
      &lt;td data-bind="text: MyNumber().toFixed(2)"&gt;&lt;/td&gt;
      &lt;td&gt;
          &lt;button class="btn" data-bind="click: $root.editItem"&gt;Edit&lt;/button&gt;&lt;/td&gt;
      &lt;td&gt;
          &lt;button class="btn btn-primary" data-bind="click: $root.enterHours"&gt;Enter Hours&lt;/button&gt;&lt;/td&gt;
  &lt;/tr&gt;
  </code></pre>
  
  <p></p>
  
  <p>Initially "MyNumber().toFixed(2)" was just "MyNumber", but I was running into an issue where "MyNumber" wouldn't show decimal places or would show more than 2 decimal places depending on the value (if the value was "7.00" it would show just "7" and if it was "7.345345" it would show the full "7.345345").  So I changed it to "MyNumber().toFixed(2)".</p>
  
  <p>That seemed to fixe the display, however now it seems that has broken the update portion:</p>
  
  <pre><code>&lt;script type="text/html" id="myEditTemplate"&gt;
      &lt;tr&gt;
          &lt;td&gt;
              &lt;input data-bind="value: MyNumber" class="table-edit" /&gt;&lt;/td&gt;
          &lt;td&gt;
              &lt;button class="btn btn-success" data-bind="click: $root.acceptItemEdit"&gt;Save&lt;/button&gt;&lt;/td&gt;
          &lt;td&gt;
              &lt;button class="btn btn-warning" data-bind="click: $root.cancelItemEdit"&gt;Cancel&lt;/button&gt;&lt;/td&gt;
      &lt;/tr&gt;
  &lt;/script&gt;
  </code></pre>
  
  <p>Here, when I attempt to save the record it will save it, but will also return the error:</p>
  
  <p>Error: Unable to parse bindings.
  Message: TypeError: Object doesn't support property or method 'toFixed';
  Bindings value: text: MyNumber().toFixed(2)</p>
  
  <p>I've tried changing the edit template so it uses: 
  ko.utils.unwrapObservable(MyNumber()).toFixed(2)
  or
  MyNumber().toFixed(2) to match the item template.  That results in no Javascript error, but also does not update the value.</p>
  
  <p>I've seen posts saying this is because "MyNumber" isn't an observable so I tried unwrapObservable().  Other than that I am not sure where I should be looking to figure out what is wrong.</p>