title: How to check whether a JavaScript function exists in Parent Window
body: <p>I am currently working on a web forms application. I have Javascript function [e.g  <code>HideWaitMessage()</code> ] in the parent window. I use <code>window.parent.HideWaitMessage()</code> from child window to access this and it works as expected. </p>
  
  <p>However, in order to avoid errors, I wanted to verify whether the function does exist in the parent window. Please advise on how I can achieve this.</p>