Javascript store client-side password across pages in memory

Question

I am working on an app that encrypts user's data with user's password on the client side without sending/sharing the password to the server. User needs to encrypt data across pages and I don't want to ask user password each time that he needs to encrypt his data.
One option I have to make my application a single-page application but it's a lot overhead. Another option is to use sessionStorage which stores data across pages for a session but I am not sure if it's as secure as an in-memory variable in a single-page app.