1. What will be the output of the following code?
setTimeout(() => {
console.log('Hello');
}, 2000);
A) Logs 'Hello' immediately
B) Logs 'Hello' after 2 seconds
C) Logs 'Hello' after 1 second
D) Throws an error
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2. Which method is used to handle the resolved value of a Promise?
A) .catch()
B) .finally()
C) .then()
D) .async()
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3. What is returned by an async function in JavaScript?
A) Undefined
B) The value returned inside the function
C) Nothing
D) A Promise
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4. What will be the output of this code?
async function greet() {
await new Promise(resolve => setTimeout(resolve, 1000));
console.log('Hello');
}
greet();
A) Logs 'Hello' after 1 second
B) Logs 'Hello' immediately
C) Throws an error
D) Logs 'undefined'
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5. Which method is used to handle errors in a Promise?
A) .then()
B) .catch()
C) .finally()
D) .await()
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6. Why is async/await often preferred over using plain Promises?
A) It is faster
B) It supports more features
C) It makes asynchronous code easier to read
D) It removes the need for error handling
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7. How can errors in async/await code be handled?
A) Using try-catch
B) Using .finally()
C) Using a callback
D) Ignoring them
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8. Which Promise method executes after both resolve and reject cases?
A) .then()
B) .finally()
C) .catch()
D) .await()
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9. What is the purpose of 'resolve' in a Promise constructor function?
A) It ignores errors
C) It completes the Promise successfully
B) It handles errors
D) It throws an error
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10. Where can the 'await' keyword be used?
A) Inside async functions
B) Anywhere in the code
C) Inside regular functions
D) Inside Promises
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11. What is a callback function in JavaScript?
A) A function that returns another function
B) A function used only in Promises
C) A function passed as an argument to be called later
D) A function that runs only once
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12. When is the 'then' method of a Promise called?
A) After the Promise is resolved
B) Before the Promise is resolved
C) Only if there is an error
D) When the Promise is rejected
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13. What does the 'async' keyword do in front of a function?
A) It pauses the function
B) It only allows Promises inside the function
C) It runs the function on a separate thread
D) It allows 'await' to be used within the function
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14. What does 'Promise.all()' do?
A) Resolves when any Promise resolves
B) Resolves when all Promises are resolved or any is rejected
C) Resolves when the last Promise is resolved
D) Waits indefinitely for all Promises
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15. What does 'Promise.race()' do?
A) Resolves only if all Promises resolve
B) Rejects if all Promises reject
C) Returns the first resolved or rejected Promise
D) Ignores any errors
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16. When does the 'finally' method of a Promise execute?
A) After the Promise resolves or rejects
B) Only after the Promise resolves
C) Only after the Promise rejects
D) Only if there is an error
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17. What is a benefit of using 'async/await' in JavaScript?
A) It makes the code run faster
B) It makes asynchronous code look like synchronous code
C) It creates a separate thread
D) It eliminates the need for error handling
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18. What does 'Promise.reject()' do?
A) Ignores any errors
B) Creates a resolved Promise
C) Creates an immediately rejected Promise
D) Creates a Promise that waits indefinitely
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19. How can you handle errors in an 'async/await' function?
A) Use a try-catch block
B) Use only 'catch' method
C) Errors cannot be handled in async functions
D) Use a 'then' block
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20. What does the 'await' keyword do?
A) It ignores Promise rejections
B) It cancels the Promise
C) It returns the Promise immediately
D) It pauses execution until the Promise resolves
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