Storing encrypted passwords client side? [closed]

I’m trying to build a javascript program that lets users encrypt strings using their passwords but I would like for this to be totally offline without requiring a server.

I’m using localstorage-slim for encrypting the strings that the user adds but I want it in a way that lets users enter the password and the localstorage data is available to them directly unencrypted for a few days. The reason I’m doing this is because I don’t want my users to be entering their password to decrypt the local storage data again and again everytime they want to get their encrypted string back.

Is it a good idea to store the password in local storage? What other alternatives are there for this?