如何获得iframe的readyState

This is my html

这是我的HTML

<div ng-if="isLoadDone" class="col-xs-12">
    <div class="text-center"><span class="fa fa-spinner fa-pulse fa-5x fa-fw margin-bottom"></span></div>
  </div>
<iframe id="appId" ng-if="isLoadDone" class="app-iframe" ng-src="{{trustedApplUrl}}"></iframe>
<div ng-if="isLoad