Often you’ll need to know if you are inside or outside the Experience/Page Editor in order perform an action. If you are on the server-side in code-behind you can check the Sitecore.Context.PageMode to determine which mode you are in. But what about at runtime? Javascript per usual can save the day! Though you can find PageModes through the Sitecore object if it is available to the browser, it may not be there. Depending on how things have been set up with your solution, the Sitecore object may not return a null as would be expected when checking to see if you can access it. Instead Sitecore may be undefined. Contrary to some examples on the web with only null checks, this quick little change in your script can correctly let you know if you are in the page editor: Just take a look to see if isPageEditor is true or false and you’re set!