React Interview Questions for Freshers (20 Real Questions with Answers)

The Virtual DOM is a lightweight copy of the real DOM. React updates it first, Diffs it with the previous version, and only updates the actual DOM where necessary (Reconciliation).

useEffect runs asynchronously after the render is committed. useLayoutEffect runs synchronously after DOM mutations but before painting, useful for measuring layout.

A HOC is a function that takes a component and returns a new component, used for reusing component logic (e.g., Auth wrapper).

Prop Drilling is passing data through many layers. Avoid it using Context API, Redux, or Component Composition.

Keys help React identify which items have changed, added, or removed. They must be unique and stable to ensure efficient updates.

Props are read-only and passed from parent to child. State is mutable and managed within the component itself.

Context provides a way to pass data through the component tree without having to pass props down manually at every level.

Hooks let you use state and other React features in functional components (e.g., useState, useEffect) without writing a class.

StrictMode is a tool for highlighting potential problems in an application. It activates additional checks and warnings for its descendants.

Use React.memo, useMemo, useCallback, code-splitting with React.lazy, and avoid anonymous functions in render.

Default imports export a single value, while named imports export multiple values. Named imports must be destructured with exact names.

A component where form data is handled by the React component state, ensuring the state is the 'single source of truth'.

Fragments (<>...</>) let you group a list of children without adding extra nodes to the DOM.

useReducer is an alternative to useState for complex state logic. It accepts a reducer function of type (state, action) => newState.

useRef returns a mutable object that persists for the full lifetime of the component. It's often used to access DOM elements directly.

JSX is a syntax extension for JavaScript that looks like HTML. It produces React 'elements'.

React uses SyntheticEvents, a cross-browser wrapper around the browser's native event system.

Lazy loading helps load components only when they are needed, reducing the initial bundle size using React.lazy and Suspense.

Mounting, Updating, and Unmounting. Functional components use useEffect to mimic these phases.

Moving state to a common ancestor component so that it can be shared between sibling components.

They cover the concepts asked in most fresher rounds. Pair them with one deployed React project you can discuss in depth — interviewers always dig into your own code.

Hooks (especially useEffect pitfalls), state management choices, keys/reconciliation, and performance (memoization, code-splitting). The questions above cover each; practise explaining the why.

Yes — CodeLadder's free AI mock interviewer runs this exact bank with voice and follow-up questions, and human mock interviews are part of Professional and Accelerator tracks.