Avoid HTML5 sessionStorage – not supported by Safari in private browsing mode!

Before deciding to use sessionStorage I did due diligence and researched browser support. http://caniuse.com/namevalue-storage shows that all modern browsers support it (less Opera Mini, who cares) As it turns out Safari desktop/mobile versions do not support sessionStorage (or localStorage) when browsing in private mote. Amplify.js is nice enough to do the check for you and amplify.store.sessionStorage will be automatically be set to null.