MERN stack interview questions for freshers

CRUD is Create, Read, Update, and Delete.

A schema defines fields, types, required flags, defaults, and indexes for a collection.

React is a library for building user interfaces from components.

JSX is a syntax that looks like HTML inside JavaScript.

Props are inputs passed from a parent and should be treated as read-only.

useState returns the current value and a setter that queues a re-render.

useEffect runs side effects after render, such as fetching data or attaching listeners.

A component is a function that returns UI from props and state.

The virtual DOM is React's in-memory tree of UI.

Class components use this.state and lifecycle methods.

key helps React identify which item changed, was added, or was removed.

Node handles many concurrent I/O waits on one thread with a non-blocking event loop.

It pins exact dependency versions for reproducible installs.

It parses JSON bodies into req.body.