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React useState() Hook Quiz

The code inside the return block of useEffect runs at which of the following action?

After component rendring
Before component unmounting
Before execution of next useEffect
Both B and C
If code is inside return block of useEffect then It is intended to run before component unmounting or before execution of next scheduled useEffect.

How many calls we can make for useEffect or useState in a single component?

Unlimited, but equal calls for both hooks
Unlimited
React does not restrict the number of calls.
Limited
Limited, but equal calls for both hooks

Which of the following is associated with the execution of useEffect in react?

Synchronous
Asynchronous
useEffect runs asynchronously, ensuring it does not block the browser from rendering during its scheduled effects.
Dual nature
User decides

Return function inside useEffect is called?

CleanUp function
It's a name for the function.
Return function
Final function
None of the above

Which of the following could be an application of return function in useEffect?

To avoid memory leak
To remove unwanted things
To reallocate resources
All of these
Return function also called cleanup function is used to clear all unwanted things after useEffect ends. So it can be applied for all these options.

Which of the following can be the possible arguments of useEffect()?

Callback function
Dependency array
None
Both
UseEffect() can take two possible arguments which are Callback function and dependency array.

What is the primary purpose of the useEffect hook in React?

To manage component state
To memoize expensive function results
To handle side effects
The useEffect hook in React is primarily used to handle side effects, such as data fetching, subscriptions, or manually changing the DOM.
To expose specific methods to parent components

When should you use the useEffect hook?

When you need to manage component state
When you want to trigger a side effect
Use useEffect when you want to perform side effects in your functional components, such as data fetching, subscriptions, or DOM manipulation.
When you need to memoize expensive function results
When you need to optimize rendering performance

What problem does the useEffect hook solve?

Improving component performance
Managing asynchronous operations
Preventing memory leaks
Handling side effects in functional components
The useEffect hook solves the problem of handling side effects in functional components, allowing developers to perform tasks like data fetching, subscriptions, or DOM manipulation.

How does the useEffect hook improve performance?

By reducing the number of component re-renders
UseEffect improves performance by allowing developers to handle side effects in a declarative way, reducing the need for manual cleanup and preventing unnecessary re-renders.
By handling asynchronous operations more efficiently
By optimizing the component's memory usage
By providing a clean way to handle side effects

What is the syntax for using the useEffect hook?

useEffect(() => {}, [])
useEffect(() => {}, {})
useEffect(() => {})
useEffect(() => {}, [dependencies])
The correct syntax for useEffect is useEffect(callbackFunction, [dependencies]), where callbackFunction is the function containing the side effect, and dependencies are optional values that, when changed, will trigger the effect to re-run.

When should you avoid using the useEffect hook?

When you need to manage component state
Avoid using useEffect for managing component state. Instead, use useState for managing state within functional components.
When you want to trigger a side effect
When you need to memoize expensive function results
When you need to optimize rendering performance

Can the useEffect hook be used to perform data fetching?

Yes, it's a recommended approach for data fetching
Yes, useEffect is commonly used for data fetching in React functional components. It allows developers to perform asynchronous operations and handle side effects in a clean and declarative way.
No, useEffect is only for managing component state
It depends on the specific use case
Data fetching should be done outside of useEffect

What is the purpose of the dependency array in the useEffect hook?

To specify which components should be rendered
To define the dependencies for the effect
The dependency array in useEffect is used to specify the dependencies for the effect. When any of the dependencies change, the effect will re-run.
To control the order of effect execution
To handle side effects within the component

What happens if you omit the dependency array in the useEffect hook?

The effect will run once after the initial render
The effect will run on every render
If you omit the dependency array in useEffect, the effect will run on every render, leading to potential performance issues and infinite loops if not handled properly.
The effect will not run at all
The behavior is undefined

Can you call useEffect inside a conditional statement?

Yes, but it's not recommended
Yes, you can call useEffect inside a conditional statement, but it's generally not recommended. This can lead to unexpected behavior and bugs, as the effect may not run when expected.
No, useEffect should always be called at the top level of the component
It depends on the specific use case
Conditional statements should be avoided in functional components

What is the purpose of returning a cleanup function in useEffect?

To clean up after the effect has been applied
The cleanup function returned by useEffect is used to clean up after the effect has been applied. This is useful for tasks like unsubscribing from subscriptions or cancelling asynchronous operations.
To cancel the effect before it's finished
To prevent memory leaks caused by the effect
To control the order of effect execution

When does the cleanup function in useEffect run?

After every render
Before the component unmounts
The cleanup function in useEffect runs before the component unmounts. This allows for proper cleanup of resources and prevents memory leaks.
After the effect has been applied
When the dependency array changes

What is the effect of having an empty dependency array in useEffect?

The effect will run once after the initial render
If you provide an empty dependency array in useEffect, the effect will run once after the initial render and will not run again for subsequent renders
The effect will run on every render
The effect will not run at all
The behavior is undefined

Can you use async/await inside the callback function of useEffect?

Yes, it's a recommended approach
Yes, you can use async/await inside the callback function of useEffect to perform asynchronous operations such as data fetching or API calls.
No, async/await should not be used inside useEffect
It depends on the specific use case
Async/await is not supported in useEffect

How do you handle cleanup for a subscription in useEffect?

Call the cleanup function returned by useEffect
To handle cleanup for a subscription in useEffect, you should call the cleanup function returned by useEffect. This ensures that resources associated with the subscription are properly released.
Use the return statement in the useEffect callback
Manually unsubscribe in the component's componentWillUnmount
There's no need to handle cleanup for subscriptions in useEffect

Is it safe to perform DOM manipulation inside the useEffect hook?

Yes, it's safe and recommended
No, DOM manipulation should be avoided in useEffect
It depends on the specific use case
Performing DOM manipulation inside the useEffect hook is generally safe, but it depends on the specific use case and whether you're working with virtual DOM or real DOM elements.
DOM manipulation is not supported in useEffect

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