JavaScript Error Handling Essentials — Questions & Answers

This quiz contains 15 questions. Below is a complete reference of all questions, answer choices, and correct answers. You can use this section to review after taking the interactive quiz above.

1. Question 1: Understanding the try Block

   Which block is used in JavaScript to wrap code that may cause an error?

   • monitor
   • catcher
   • trap
   • caught
   • try
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   Correct answer: try

2. Question 2: Correct Catch Block Syntax

   What is the correct way to start a catch block after a try block in JavaScript?

   • catching(error)
   • catch: error
   • catch(error)
   • catcher(error)
   • catch error
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   Correct answer: catch(error)

3. Question 3: Purpose of finally Block

   Which JavaScript block is always executed after try and catch, regardless of whether an error occurred?

   • complete
   • finish
   • done
   • end
   • finally
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   Correct answer: finally

4. Question 4: Using throw Statement

   Which statement is used in JavaScript to manually trigger an error?

   • raise
   • rise
   • throw
   • emit
   • error
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   Correct answer: throw

5. Question 5: Error Object Basics

   What does the built-in Error object in JavaScript represent?

   • A log entry
   • An exception that is thrown
   • A successful result
   • A function callback
   • A warning message
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   Correct answer: An exception that is thrown

6. Question 6: Accessing Error Message

   After an error is caught, which property of the error object contains the error message?

   • msg
   • reason
   • message
   • detail
   • description
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   Correct answer: message

7. Question 7: Handling Errors Gracefully

   What is one main advantage of using try/catch in JavaScript?

   • It disables error logging
   • It automatically fixes syntax errors
   • It allows handling errors without stopping script execution
   • It slows down the program intentionally
   • It checks for memory leaks
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   Correct answer: It allows handling errors without stopping script execution

8. Question 8: Custom Error Throwing Example

   What happens when the following code is executed? throw new Error('Invalid input');

   • A warning is displayed but code continues
   • An error is created and thrown with the message 'Invalid input'
   • The code is ignored and nothing happens
   • The error is silently logged
   • JavaScript restarts the program
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   Correct answer: An error is created and thrown with the message 'Invalid input'

9. Question 9: Catching Specific Error Types

   In JavaScript, which error object is specifically thrown for references to undefined variables?

   • ValueError
   • TypeError
   • ErrorRef
   • ReferenceError
   • SyntaxError
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   Correct answer: ReferenceError

10. Question 10: Understanding Error Propagation

    If an error is not caught inside a try/catch block, what typically happens in JavaScript?

    • The script pauses and resumes
    • The error is fixed automatically
    • A custom handler always runs
    • The error propagates up and may stop script execution
    • The code jumps to the start
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    Correct answer: The error propagates up and may stop script execution

11. Question 11: Order of Execution

    Given a try/catch/finally structure, which block is always executed regardless of errors?

    • lastly
    • finally
    • finish
    • always
    • done
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    Correct answer: finally

12. Question 12: Creating Custom Errors

    How do you create a custom error type in JavaScript?

    • By extending the Error class
    • By defining an error in catch
    • By setting error.custom = true
    • By calling createError()
    • By using 'makeError'
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    Correct answer: By extending the Error class

13. Question 13: Handling Syntax Errors

    Can a try/catch statement catch syntax errors that occur during JavaScript parsing?

    • No, syntax errors occur before try/catch runs
    • Yes, but only with custom errors
    • Only with the 'catchAll' method
    • Only if using finally
    • Yes, always
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    Correct answer: No, syntax errors occur before try/catch runs

14. Question 14: Accessing Error Name

    Which property of the error object in JavaScript gives the type of error?

    • name
    • class
    • category
    • error
    • type
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    Correct answer: name

15. Question 15: Error Handling in Asynchronous Code

    When using Promises, which method is typically used to handle errors instead of try/catch?

    • catcher()
    • trap()
    • error()
    • catch()
    • throw()
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    Correct answer: catch()