How can you give your mobile web app an install screen?

Question

Similar to how forecast.io does it - if you visit their website on your phone. this shows up:

Once you add it to your home screen, the rest of the app becomes available.

Answer 1

window.navigator.standalone

will result in true if you have launched from the Home Screen or false if the page is open in a browser. Documented very nicely by Apple in their Developer Docs and works with OS 2.1 and up.

For example:

if (window.navigator.standalone) {
    // fullscreen mode

}