JavaScript Essentials 1 | JSE1 – Module 6 Test Exam Answers Full Score 100%

JavaScript Essentials 1 | JSE1 – Module 6 Test Exam Answers Full Score 100% 2024

1. Which of the following is a syntax error?

   • Attempting to modify the value of a constant.
   • Missing parenthesis ending a condition in an if statement.
   • Attempting to call a non-existent function.
   • Attempting to read a value from a variable that we have not previously declared.
     

     Explanation & Hint: In JavaScript, when using an if statement, the condition must be enclosed in parentheses. If you omit the closing parenthesis, it will result in a syntax error.

2. Logical errors that we make while writing a program are not indicated by the interpreter. Why?

   • The interpreter does not indicate errors while the program is running, because it detects them before the program runs (it does not allow the program to run).
   • The interpreter ignores logical errors, because they do not affect the result of the program in any way.
   • It results from the default settings of the interpreter, although we can modify these settings so that logical errors are also pointed out.
   • The interpreter is unable to identify logical errors because they are not related to either the syntax or the semantics of the JavaScript language.

   • Explanation & Hint: Logical errors are not indicated by the interpreter because they do not violate the syntax or grammar rules of the programming language. Instead, logical errors occur when the program does not produce the desired or expected output due to incorrect or flawed logic in the code. The role of the interpreter or compiler is to execute the code according to the syntax and rules of the language. It checks for syntax errors and ensures that the code follows the language’s grammar.

3. Analyze the code below:

   "let x = 10";
   console.log(x);

   What exception will be thrown as a result of its execution attempt?

   • RangeError
   • TypeError
   • SyntaxError
   • ReferenceError

   • Explanation & Hint: The code will throw an exception when executed: Uncaught ReferenceError: x is not defined.

4. Analyze the following code:

   let x 10;
   console.log(x);

   What exception will be thrown as a result of its execution attempt?

   • TypeError
   • RangeError
   • ReferenceError
   • SyntaxError

   • Explanation & Hint: The code contains a syntax error. In the line let x 10;, there is a missing assignment operator (=) between x and 10, which leads to a syntax error.

5. Analyze the following code:

   let x = 10;
   ocnsole.log(x);

   What exception will be thrown as a result of its execution attempt?

   • SyntaxError
   • ReferenceError
   • TypeError
   • RangeError

   • Explanation & Hint: JavaScript interpreter will throw a ReferenceError and display an error message indicating that ocnsole is not defined. The error occurs because the interpreter cannot find a variable or function named ocnsole, and it is unable to execute the code as intended.

6. Analyze the following code:

   const x = 10;
   onsole.log(x);
   x += 10;

   What exception will be thrown as a result of its execution attempt?

   • ReferenceError
   • SyntaxError
   • ReferenceError and TypeError
   • TypeError

   • Explanation & Hint: If you attempt to execute the code with the errors (onsole.log(x) and x += 10;), the JavaScript interpreter will throw a ReferenceError. The ReferenceError will occur due to the typo in onsole.log(x). The error message will indicate that onsole is not defined.

7. Analyze the following code:

   const x = 10;
   x = 20;

   What exception will be thrown as a result of its execution attempt?

   • ReferenceError
   • TypeError
   • RangeError
   • SyntaxError

   • Explanation & Hint: If you attempt to execute the code the JavaScript interpreter will throw a TypeError. The TypeError will occur because you are trying to reassign a value to a constant variable, which is not allowed. Constants are immutable and their values cannot be changed once assigned.

8. Analyze the following code:

   try {
   ocnsole.log("start");
   } catch (error) {
   console.log("error");
   }
   console.log("end");

   What will happen as a result of its execution?

   • The operation of the program will be interrupted and the console will display the default message "Uncaught ReferenceError: ocnsole is not defined".
   • The console will display the following words on successive lines error, end.
   • The console will display the following words on successive lines: start, error, end.
   • The console will display the following words on successive lines: start, end.

   • Explanation & Hint: The error message “Uncaught ReferenceError: ocnsole is not defined” in JavaScript indicates that there is a reference to an undefined variable or identifier. In the specific case, the error is caused by the typo in the code where ocnsole.log(“start”); is written instead of console.log(“start”);. JavaScript is treating ocnsole as a variable or identifier, but it has not been defined anywhere in the code. As a result, a ReferenceError is thrown.

9. Analyze the following code:

   try {
   ocnsole.log("start");
   } catch (error) {
   console.log("error");
   } finally {
   console.log("end");
   }

   What will happen as a result of its execution?

   • The words start, error, end will appear in the console on successive lines.
   • The word error will appear in the console.
   • The following words will appear in the console: error, end.
   • The following words will appear in the console: start, end.

   • Explanation & Hint: In the code, there is a typo in the console.log() function, which should be console.log(“start”);, not ocnsole.log(“start”);. The try block will be executed, which includes the statement console.log(“start”);. However, since there is a typo in the code, a ReferenceError will occur when trying to access the undefined variable ocnsole. This error will cause the execution of the try block to be interrupted. Since an error occurred within the try block, the execution will be transferred to the catch block. The statement console.log(“error”); will be executed, printing the message “error” to the console. This is a way to handle and report the error. After the catch block is executed, the finally block will be executed regardless of whether an error occurred or not. The statement console.log(“end”); will be executed, printing the message “end” to the console. In this case, even though an error occurred, the finally block is still executed, allowing you to perform necessary actions regardless of the error.

10. Analyze the following code:

    try {
    console.log("start");
    } catch (error) {
    console.log("error");
    } finally {
    console.log("end");
    }

    What will happen as a result of its execution?

    • The word error will appear in the console.
    • The following words will appear in the console: start, end.
    • The following words will appear in the console: start, error, end.
    • The following words will appear in the console: error, end.

    • Explanation & Hint: The try block will be executed, which includes the statement console.log(“start”);. This statement will print “start” to the console without any errors. Since no error occurred within the try block, the catch block will be skipped entirely. After the try block is executed, the finally block will be executed regardless of whether an error occurred or not. The statement console.log(“end”); will be executed, printing “end” to the console. The finally block ensures that the specified code is always executed, regardless of whether an error occurs or not. It is commonly used to perform cleanup or finalize operations. In this case, since no error occurred, the finally block is still executed, allowing you to perform necessary actions at the end of the code execution.

11. What is the name of the place where program code execution is halted?

    • pausepoint
    • exitpoint
    • stoppoint
    • breakpoint

    • Explanation & Hint: A breakpoint is a designated point in the code where the program execution is intentionally paused to allow for debugging, analysis, and inspection of variables, state, and flow of the program. Developers can set breakpoints in their code to halt the execution at specific locations to examine the program’s behavior and troubleshoot issues.

12. Using the debugger, we insert a breakpoint in the code at which, after running the program, we stop. In the debugger, we find a Step button among the step-by-step operation options. What does pressing it do?

    • The program will be executed to the end, regardless of whether there are more breakpoints in the rest of the code or not.
    • The program will execute to the end or to the next breakpoint.
    • The program will be restarted from the first instruction.
    • Exactly one instruction immediately after the breakpoint will be executed and the program will be paused again.

    • Explanation & Hint: Pressing the “Step” button in the debugger allows you to execute the program code one step at a time, progressing through the code line by line. The “Step” operation is useful for debugging and understanding how the code is executing, especially in complex scenarios or when you want to trace the program’s flow.

13. Where in the debugger can you find the information about the currently called functions in your program?

    • In the call stack window.
    • In the console.
    • In the watch window.
    • There is no access to such information.

    • Explanation & Hint: In a debugger, you can typically find information about the currently called functions in a panel or window called the “Call Stack” or “Call Stack Trace”. The Call Stack usually displays the names of the functions, along with additional information such as the file and line numbers where the function calls were made. By inspecting the Call Stack, you can track the flow of execution through different function calls and identify which functions are currently active.

14. You want to measure how long a certain piece of code executes. In order to do so, it is enough to precede the code fragment with:

    • the command console.time("counter") and end with console.timeEnd("counter").
    • the command console.time("start") and end with console.time("end").
    • the command console.timeStart("counter") and end with console.timeEnd("counter").
    • the command timeStart() and end with timeEnd().

    • Explanation & Hint: To measure the execution time of a code fragment in JavaScript, you can use the console.time() and console.timeEnd() methods. Precede the code fragment with console.time(“counter”). End the code fragment with console.timeEnd(“counter”).