Almost every app you use (Instagram, WhatsApp, Shopee, even your school's attendance system) is built on four basic actions. Once you can spot them, you can build them too.
real apps do exactly this: just with a server instead of your browser
New data gets saved for the first time.
Like: posting a new photo, sending a message, registering a new student.
Existing data is shown to you, unchanged.
Like: scrolling your feed, opening a chat, checking a class list.
Existing data is edited, not replaced entirely.
Like: editing your bio, renaming a group chat, marking someone late instead of absent.
Data is taken away completely.
Like: unsending a message, deleting a post, removing a student who transferred out.
In a real app, data is saved on a server in a database. Today's demo saves data using your browser's own built-in storage (localStorage) instead: no server needed, but the exact same CRUD logic. What you learn here transfers directly to real databases later.