I suggest creating an entity for your temporary data associated either to the user or to the session in Mendix. This is a bit more reliable as Mendix can carry sessions between browser sessions, maintains them a while after the browser is closed and re-activates them if the user re-opens the page.
You can then retrieve and use them in any MF logic.
Hope this helps
Either use entities (Non Persistent) as Dragos Vrabie describes or you can take a look at the example in the appstore / github on LocalStorage https://github.com/cdcharlebois/mxLocalStorage