Is there a way to display text if Cydia is installed?

I am making a mobile website and I want to know if there is a possible way to write text on the page if Cydia is i开发者_JS百科nstalled? Preferably in Javascript. I'm guessing it would be a variable and an if/else statement.

You can test if the page is opened inside Cydia, but it not if Cydia is installed.

You can do this with matching the useragent string with Cydia.

Well this might be possible, but I'm not sure if someone could make it.

But you can open it with a link to cydia://.

If you can check that the link is valid or something, thare might be a way.