how to get the device to use in an if statement

HI all,

Does someone know how to use the site of a screen or the device (mobile) a user is using, so I can use it in an if statement when directing to another screen.

Or, does someone know how to scale a popup, that it is fullscreen on a mobile device?

Thank you.

when using jquery:

you can also check useragents possible.

with silkUI you can also check with some actions.

btw, popups on a mobile device is a no-no imho!