title: Angular Custom Components
body: <p>I am working with Angular 4 in my application.    </p>
  
  <p>How to run a component always in background , and that should not be visible untill we pass some values to that component/directive.  when we pass some values to component/directive which is running in background it should be open on top current component(current view page) some thing like alert message.  <strong>it should not disturb current flow of execution.</strong></p>