React Questions

To enforce the data type of props

To manage component state

To handle user events

To style components

const Welcome = () => { ... };

function Welcome(props) { ... }

let Welcome = (props) => { ... }

class Welcome extends React.Component { ... }

The component will re-render, but the state change won't be reflected.

Nothing will happen; the state will remain unchanged.

An error will be thrown, and the application will crash.

The component will re-render, and the state change will be reflected correctly.

Arguments passed to a component

Lifecycle methods of a component

Functions to update the UI

Internal data of a component

By modifying this.props object

Using the useState hook

By calling this.setState({ new state })

Using this.state = { new state } directly

By using a ref to the DOM element and accessing its event listeners

Through the nativeEvent property of the synthetic event object

By directly using event.target or event.currentTarget

React doesn't provide access to the original DOM event; it's completely abstracted.

React doesn't provide a way to access the triggering element

Using this keyword inside the event handler

By passing the element as an argument to the event handler

As a property of the event object (e.g., event.target)

To handle form submissions

To perform side effects like data fetching, DOM manipulation, or subscriptions

To render components conditionally

To manage state within a component

Functional components are used for complex UI, while class components are used for simple UI.

Class components can have state and lifecycle methods, while functional components cannot.

Functional components are written in JavaScript, while class components are written in JSX.

There is no difference; both are interchangeable.

Using inline event handlers like onClick={handleClick}

Using the addEventListener method like in vanilla JavaScript

React components don't handle events directly; you must use a library.

Defining separate event handler methods within the component