Knockout unable to process binding

问题:

How do I bind a text when it is undefined? For example name is not available:

<table id="recordTbl" data-bind="visible: records().length &gt; 0" class="table">
  <thead>
    <tr>
      <th class="col-md-4">ID</th>
      <th class="col-md-4">Name</th>
    </tr>
  </thead>
  <tbody data-bind="foreach: records">
    <tr>
      <td data-bind="text: id"></td>
      <td data-bind="text: name"></td>
    </tr>
  </tbody>
</table>

I get this error:

Uncaught ReferenceError: Unable to process binding "text: function (){return name }"
Message: name is not defined 

回答1:

You can you the $data binding context property which always represents the current view model to access the name through it:

  <tbody data-bind="foreach: records">
    <tr>
      <td data-bind="text: id"></td>
      <td data-bind="text: $data.name"></td>
    </tr>
  </tbody>

With this approach KO won't throw an exception if one of the items in the records does not have a name property.

Without the $data the identifier named name is undefined. However $data.name is always a valid expression it just returns undefined if the current view model does not have a property named name.