title: Knockout: How to pass the Checkbox "checked" value to a Click handler function?
body: <p>I want to send "true/false" value to a click handler, depending if the checkbox is checked or not. </p>
  
  <ul>
  <li>On check, it should send a 3rd parameter (isChecked) with value "true".</li>
  <li>On uncheck, it should send a 3rd parameter (isChecked) with value "false".</li>
  </ul>
  
  <p>I'm sure this is really easy, but I'm having a hard time figuring it out. 
  Here is the input element: </p>
  
  <pre><code>&lt;input class="cards-view--item-checkbox pull-right" type="checkbox"
   data-bind="value: universalParcelId, checked: $parent.isChecked, checkedValue: true, 
   click: function(data, event, isChecked) { 
   return $root.addUPIDtoArray(data, event, $parent.isChecked()) }"&gt;
  </code></pre>
  
  <p>Click handler:</p>
  
  <pre><code>addUPIDtoArray: function (data, event, isChecked) {
      var self = this;
  
      self.isChecked = ko.observable();
  
      // If checked
      if(isChecked()) {
          self.upIDArray.push(data.universalParcelId);
          self.upIDWithIndexArray.push({
              universalParcelID: data.universalParcelId,
              searchResultIndex: data.searchResultIndex
          });
  
          // If unchecked
      } else if(!isChecked()) {
          // remove from array
      }
  
      return true; // allow the default "click" action, which is checking the box with a "check"
  },
  </code></pre>
  
  <p>I thought i could use the "event" parameter, but for some reason it is coming through as a jQuery.event, instead of a regular DOM event. So I decided for the 3rd parameter. But it just doesn't work like this: gives error <code>$parent.isChecked is not a function</code> </p>
  
  <p>Any ideas?</p>