title: why is knockout computed only called on input checkbox being cleared
body: <p>When the initial value is true results in the ko.computed being called only on false new values missing all true new values.</p>
  
  <p>Likewise, if the initial value is false, then ko.computed is only called on new true values.</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>$(function () {
  
              function getFormattedDate() {
                  var date = new Date();
                  var str = date.getFullYear() + "-" + (date.getMonth() + 1) + "-" + date.getDate() + " " + date.getHours() + ":" + date.getMinutes() + ":" + date.getSeconds();
  
                  return str;
              }
  
              var ViewModel = function (initial_value) {
  
                  var self = this
  
                  self.debug_logs = ko.observableArray()
  
                  self._my_checked = initial_value
                  self.my_checked = ko.computed({
                      read: function () {
                          self.debug_logs.push({ log: "Reading value to " + self._my_checked + " " + getFormattedDate() })
                          return self._my_checked
                      },
                      write: function (value) {
                          self.debug_logs.push({ log: "Setting value to " + value + " " + getFormattedDate() })
  
                          self._my_checked = value
                      }
                  })
              }
  
              ko.applyBindings(new ViewModel(true))
  
          })</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"&gt;&lt;/script&gt;
  &lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"&gt;&lt;/script&gt;
  
      &lt;div&gt;
           &lt;input type="checkbox" data-bind="checked: my_checked" /&gt;  
  
          &lt;ol data-bind="foreach:debug_logs"&gt;
              &lt;li data-bind="text:log"&gt;&lt;/li&gt;
          &lt;/ol&gt;
      &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>I need the computed to be called on both clearing and setting of the checkbox.  This will drive other functionality not shown.</p>
  
  <p>Thank you in advance</p>