Is there a preferred JavaScript method for detecting screen size in a browser?

Question

I have been looking at way to detect what screen size I am working with for a website. i.e. iPhone, desktop, tablet, etc.

So far I have come across quite a few methods. I am just looking to see if there is a preferred method, one that is more universal, etc. I realize there is rarely a one size fits all method. Just looking for the best.

If it makes a difference, the website will be a very minimalistic website. It's more of an add-on page for an app. So there will no bells and whistles on it.

window.innerWidth
...
screen.width 
...
document.body.clientWidth
...
window.outerWidth;