title: why angularJs $watch only run once
body: <p>codes in the watch run only once .
  how can i fix it  ? </p>
  
  <pre><code> this.$rootScope.$watch('tabType', () =&gt; {
              if (this.$rootScope["tabType"] === TabType.Sent) {
                  this.$scope.refreshSentList();
              } else if (this.$rootScope["tabType"] === TabType.Archive) {
                  this.$scope.refreshArchiveList();
              } else if (this.$rootScope["tabType"] === TabType.Inbox) {
                  this.$scope.refreshInboxList();
              } else if (this.$rootScope["tabType"] === TabType.Snooz) {
                  this.$scope.refreshSnoozList();
              } else if (this.$rootScope["tabType"] === TabType.Trash) {
                  this.$scope.refreshTrashList();
              }
          },true);
  </code></pre>