JavaScript Essentials 1 JSE1 Module 4 Test Exam Answers 100%

JavaScript Essentials 1 (JSE) | JSE1 – Module 4 Test Exam Answers Full 100% 2023 2024

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4.2 Module 4 Completion – Module Test Exam Answers Full 100% 2023 2024

The condition `if( a >= 0 )` can be replaced by the condition:

if (a > 0 || a == 0);
if (a > 0 && a == 0);
if (0 < a);

if (!(a > 0 && a == 0));

Explanation & Hint:

The condition if( a >= 0 ) can be replaced by the condition: if (a > 0 || a == 0);

The replacement condition checks if “a” is greater than 0 or equal to 0. This is equivalent to the original condition a >= 0 because if “a” is greater than or equal to 0, it satisfies the condition a > 0 || a == 0.

The condition `if (!a)` can be replaced by the condition:

if (a);
if (!!a);
if (a === false);
if (a == false);

Explanation & Hint:

The condition if (!a) in JavaScript can be replaced by the condition if (a == false). In JavaScript, the ! operator is the logical NOT operator and negates the truthiness of a value. It converts the value to its boolean opposite.

We want to rewrite the following code snippet using the conditional operator:

let name;
if (test) {
    name = "Alice";
} else {
    name = "Bob";
}

Which notation is correct?

let name = test : "Alice" ? "Bob";
let name = test ? "Alice" : "Bob";
let name = if test ? "Alice" : "Bob";
let name = (test)("Alice")("Bob");

Explanation & Hint:

In the conditional (ternary) operator, the condition test is evaluated. If test is truthy, the expression before the ? (in this case, “Alice”) is assigned to name. If test is falsy, the expression after the : (in this case, “Bob”) is assigned to name. By using the conditional operator, you can simplify the if-else statement into a single line. The value assigned to name depends on the condition test, resulting in the same outcome as the original if-else statement.

Which of the following operators is a ternary one?

An assignment operator =.
A conditional operator ? :.
A typeof operator.
An increment operator ++.

Explanation & Hint:

The ternary operator in JavaScript is represented by the ? and : symbols. It is the only ternary operator in JavaScript. The ternary operator takes the following form: condition ? expression1 : expression2 It evaluates the condition and returns expression1 if the condition is truthy, or expression2 if the condition is falsy.

Review the following code:

let x = 100;
if (x < 100)
    x = 20;
console.log(x)

What will be displayed in the console as a result of its execution?

nothing
100
20
false

Explanation & Hint:

Here’s the breakdown of the code:

let x = 100; – Declares a variable x and initializes it with the value 100.if (x < 100) – Checks if the value of x is less than 100. However, since x is equal to 100, the condition evaluates to false.

x = 20; – Inside the if block, assigns the value 20 to x. However, since the condition in the if statement is false, this line of code will not be executed.
console.log(x); – Prints the value of x to the console. Since x is still 100, it will be displayed as 100 in the console.

The value of x remains unchanged because the if statement condition is not met, and the assignment x = 20 is not executed.

Review the following code:

if (counter <= 10) {
    if (counter >= 10) {
     console.log(1);
    }
}

We can replace it using:

if (true) console.log(1);
if (false) console.log(1);
if (counter >= 10) console.log(1);
if (counter == 10) console.log(1);

Explanation & Hint:

The given code snippet can be simplified by removing the nested if statement, as it does not have any effect on the logic. In the simplified code, we directly check if the counter variable is equal to 10 using a single if statement. If the condition is met, meaning counter is exactly 10, then 1 will be logged to the console.

Review the following code snippet:

if (counter <= 10 && show === false) {
    console.log("test");
}

What values can the `counter` and `show` variables have so that the console displays `"test"` as a result of code execution?

counter: 11, show: false
counter: 10, show: true
counter: 9, show: true
counter: 10, show: false

Explanation & Hint:

In this case, both conditions are met: counter is equal to 10 (less than or equal to 10), and show is false. Therefore, the code block inside the if statement will be executed, and “test” will be logged to the console. It’s important to note that these are just example values, and you can have other valid combinations of counter and show values that satisfy the conditions. As long as counter is less than or equal to 10 and show is false, the code block will be executed and “test” will be logged to the console.

The `switch` statement:

allows you to change the program mode to debug mode.
is a conditional statement that allows different actions to be taken depending on the value stored in the indicated variable.
is a conditional statement that works identically to the if statement.
is not present in the JavaScript language.

Explanation & Hint:

In JavaScript, the switch statement provides a way to perform different actions based on different conditions. It allows you to choose a specific case from multiple options and execute the corresponding code block. The switch statement provides a more concise way to handle multiple conditions compared to using multiple if statements. It can improve code readability and maintainability, especially when dealing with a large number of potential cases.

Analyze the code below:

if (counter === 10) {
    console.log("abc");
}

How can we write the same condition using the `switch` statement?

case(counter) {
  switch 10:
     console.log("abc")
};

switch(counter) {
  case ? 10 :
     console.log("abc")
};

switch(counter) {
  case 10:
     console.log("abc")
};

switch(counter) 
  case 10:
     console.log("abc");

Explanation & Hint:

To write the same condition using the switch statement, you can set up a switch statement with a single case that checks if the counter variable is equal to 10. In this case, the switch statement is set up with the counter variable as the expression to evaluate. The case 10 is defined to match when the value of counter is equal to 10. Inside the case block, the code console.log(“abc”) is executed. The switch statement provides an alternative way to handle multiple conditions, especially when there are more than two possible values to compare against.

Which sequence of `if ... else` statements is incorrect?

if ... else ...
if ... else if ...
if ... else if ... else if...
if ... else ... else if ...

Explanation & Hint:

The sequence allows you to evaluate multiple conditions in a cascading manner. The first condition is checked, and if it is true, the corresponding code block is executed. If the first condition is false, the next condition is checked, and so on. If none of the conditions are true, the code block within the else statement is executed. The incorrect sequence “if…else…else if” does not follow the correct syntax and can lead to unexpected behavior or syntax errors in JavaScript.

Which of the following is not a loop instruction in JavaScript?

for ... in
do ... while
for ... of
if ... else

Explanation & Hint:

The “if … else” statement is not a loop instruction in JavaScript. The “if … else” statement is a conditional statement used to perform different actions based on a condition. It does not involve repetition or looping over a set of values or elements. It allows you to specify different code blocks to be executed based on whether a condition is true or false.

Which of the following loop instructions is intended only to loop through all the keys of the indicated object?

for ... of
if ... else
for ... in
do ... while

Explanation & Hint:

The loop instruction intended only to loop through all the keys of the indicated object is the “for … in” loop. The “for … in” loop in JavaScript is used to iterate over the properties (keys) of an object. It allows you to loop through each enumerable property of an object and execute a block of code for each property. The loop variable represents each key in the object during each iteration.

If we want to display all the elements of the `days` array in reverse order (starting from the last element) then we can do this using the statement:

for(let i = days.length - 1; i > 0; i--)
     console.log(days[i]);

for(let i = days.length; i > 0; i--)
     console.log(days[i]);

for(let i = days.length; i > 0; i--)
     console.log(i);

for(let i = days.length - 1; i >= 0; i--)
     console.log(days[i]);

Explanation & Hint:

A for loop is used to iterate over the elements of the days array in reverse order. The loop starts from the index of the last element (days.length – 1) and decrements the index (i) by 1 in each iteration until it reaches 0. Inside the loop, console.log(days[i]) is used to display each element of the array. By iterating in reverse order, you can effectively display all the elements of the days array starting from the last element and going towards the first element.

Analyze the following code:

let a = 10;
do {
    console.log(a--);
} while (a > 3);

Which statement can replace the `do ... while` from the example above?

while (a > 4)
     console.log(--a);

while (a > 2)
     console.log(--a);

while (a > 3)
     console.log(a--);

while (a >= 3)
     console.log(a--);

Explanation & Hint:

The while loop has the same condition as the do…while loop, a > 3. The loop will continue executing as long as the condition is true. The code inside the loop is the same: console.log(a–), which displays the value of a and then decrements it by 1. The difference between do…while and while loops is that a do…while loop executes the code block at least once, even if the condition is initially false. In contrast, a while loop checks the condition first and only executes the code block if the condition is true. Since the do…while loop in the given code will always execute at least once (as a starts with a value greater than 3), it can be replaced with a while loop without affecting the output.

Analyze the following code:

for (let x = 10; x > 1; x -= 2)
console.log("hello");

How many times will `"hello"` be displayed in the console as a result of its execution?

Explanation & Hint:

The for loop is initialized with x set to 10. The loop condition is x > 1, and the loop’s iteration statement is x -= 2, which subtracts 2 from x in each iteration. The loop will continue executing as long as x is greater than 1. In each iteration, the code console.log(“hello”) is executed, which displays “hello” in the console. The loop starts with x = 10, and it will execute when x is greater than 1, subtracting 2 from x in each iteration. After the 5th iteration, x becomes 2, and the loop condition x > 1 evaluates to false, causing the loop to terminate.

We store an array of animal names in the `animals` variable (e.g. `let animals = ["dog", "cat", "hamster", "rabbit"];`).

Which of the following statements will display exactly two names from the array?

for (let i =3 ; i < animals.length; i++)
     console.log(animals[i]);

for (let n in animals)
     console.log(n);

for (let n of animals)
     console.log(n);

for (let i = 0; i < animals.length; i+=2)
     console.log(animals[i]);

Explanation & Hint:

In this code, the for loop starts at index 3 (the fourth element) of the animals array (i = 3), and continues iterating as long as i is less than the length of the animals array (i < animals.length). In each iteration, it logs the value at index i of the animals array (console.log(animals[i])). Since the for loop starts at index 3 and continues until the end of the array, it will display exactly two names from the array, assuming there are at least two elements in the array after index 3.

Examine the following code:

for (let a = 5; a > 1; a--) {
    console.log(a);
}
;

Which statement can replace the for from the example above?

let a = 1; while (a < 5)
     console.log(a++);

let a = 5; while (a > 1)
     console.log(a++);

let a = 6; while (a >= 1)
     console.log(a--);

let a = 5; while (a > 1)
     console.log(a--);

Explanation & Hint:

A while loop is used to achieve the same iteration logic as the for loop. The while loop has the condition a > 1, which is the same as the for loop’s condition. The loop will continue executing as long as a is greater than 1. Inside the loop, console.log(a–) is used to display the value of a and then decrement it by 1. This is equivalent to the iteration statement in the for loop, which is a–.

Examine the following code:

for (let a = 4; a < 4; a++) {
    console.log("test");
}

How many times will `"test"` be displayed in the console as a result of its execution?

1
4
3
It will not be displayed at all.

Explanation & Hint:

The for loop in the code initializes a with the value of 4. The loop condition a < 4 is evaluated before each iteration. Since a is already equal to 4, the loop condition is false, and the loop will not execute. Therefore, “test” will not be displayed in the console at all because the loop is not executed.

Examine the following code:

let car = {make: "Citroen", model: "DS"};
for (let f in car)
console.log(f);

What will appear on the console as a result?

"Citroen" "DS"
"make: Citroen" "model: DS"
"car"
"make""model"

Explanation & Hint:

The code utilizes a for…in loop to iterate over the properties of the car object. In each iteration, the loop variable f represents the current property name being iterated. The console.log(f) statement logs the value of f to the console. Since the car object has two properties, “make” and “model”, the for…in loop will iterate over these properties, and the respective property names will be displayed in the console: “make” and “model”.

Examine the following code:

let steps = [3, 2, 1];
for (let n of steps)
console.log(n);

What will appear on the console as a result?

1 2 3
"[3, 2, 1]"
3 2 1
0 1 2

Explanation & Hint:

The code utilizes a for…of loop to iterate over the elements of the steps array. In each iteration, the loop variable n represents the current element of the array being iterated. The console.log(n) statement logs the value of n to the console. Since the steps array contains three elements [3, 2, 1], the for…of loop will iterate over each element, and the respective values will be displayed in the console: 3, 2, and 1.

JavaScript Essentials 1 (JSE) | JSE1 – Module 4 Test Exam Answers Full 100% 2023 2024

4.2 Module 4 Completion – Module Test Exam Answers Full 100% 2023 2024

The condition if( a >= 0 ) can be replaced by the condition:

The condition if (!a) can be replaced by the condition:

We want to rewrite the following code snippet using the conditional operator:

Which notation is correct?

Which of the following operators is a ternary one?

Review the following code:

What will be displayed in the console as a result of its execution?

Review the following code:

We can replace it using:

Review the following code snippet:

What values can the counter and show variables have so that the console displays "test" as a result of code execution?

The switch statement:

Analyze the code below:

How can we write the same condition using the switch statement?

Which sequence of if ... else statements is incorrect?

Which of the following is not a loop instruction in JavaScript?

Which of the following loop instructions is intended only to loop through all the keys of the indicated object?

If we want to display all the elements of the days array in reverse order (starting from the last element) then we can do this using the statement:

Analyze the following code:

Which statement can replace the do ... while from the example above?

Analyze the following code:

How many times will "hello" be displayed in the console as a result of its execution?

We store an array of animal names in the animals variable (e.g. let animals = ["dog", "cat", "hamster", "rabbit"];).

Which of the following statements will display exactly two names from the array?

Examine the following code:

Which statement can replace the for from the example above?

Examine the following code:

How many times will "test" be displayed in the console as a result of its execution?

Examine the following code:

What will appear on the console as a result?

Examine the following code:

What will appear on the console as a result?

The condition `if( a >= 0 )` can be replaced by the condition:

The condition `if (!a)` can be replaced by the condition:

What values can the `counter` and `show` variables have so that the console displays `"test"` as a result of code execution?

The `switch` statement:

How can we write the same condition using the `switch` statement?

Which sequence of `if ... else` statements is incorrect?

If we want to display all the elements of the `days` array in reverse order (starting from the last element) then we can do this using the statement:

Which statement can replace the `do ... while` from the example above?

How many times will `"hello"` be displayed in the console as a result of its execution?

We store an array of animal names in the `animals` variable (e.g. `let animals = ["dog", "cat", "hamster", "rabbit"];`).

How many times will `"test"` be displayed in the console as a result of its execution?