JavaScript Control Flow and Loops.

What is the basic syntax of an if statement in JavaScript?

• if { condition } // code to execute

• if (condition) // code to execute

• if condition { // code to execute }

• if (condition) { // code to execute }

Answer explanation

The correct syntax for an if statement in JavaScript is 'if (condition) { // code to execute }'. This format includes parentheses around the condition and curly braces for the code block, making it the proper structure.

How does an else if statement differ from a simple if statement?

• An 'else if' statement can check multiple conditions, while a simple 'if' statement checks only one.

• An 'else if' statement is used only in loops.

• An 'else if' statement cannot be used in nested conditions.

• A simple 'if' statement can check multiple conditions.

Answer explanation

An 'else if' statement allows for checking multiple conditions in sequence, while a simple 'if' statement evaluates only one condition at a time. This makes 'else if' useful for handling complex decision-making scenarios.

Provide an example of a switch statement that checks for a day of the week.

• switch(day) { case 'Monday': console.log('Start of the week'); break; case 'Tuesday': console.log('Second day of the week'); break; case 'Wednesday': console.log('Midweek'); break; case 'Thursday': console.log('Almost there'); break; case 'Friday': console.log('End of the work week'); break; case 'Saturday': console.log('Weekend!'); break; case 'Sunday': console.log('Rest day'); break; default: console.log('Invalid day'); }

• switch(day) { case 'January': console.log('Start of the year'); break; }

• switch(day) { case 'Monday': console.log('Midweek'); break; }

• switch(day) { case 'Friday': console.log('Start of the weekend'); break; }

Answer explanation

The correct switch statement checks for all days of the week, providing specific messages for each day. The other options either check for a month or incorrectly label days, making them invalid for the question.

What will the following code output? if (x === 5) { console.log('Five'); } else { console.log('Not Five'); }

• 'Not Five' if x is 5

• Depends on the value of x; 'Five' if x is 5, 'Not Five' otherwise.

• 'Five' if x is 0

• 'Five' if x is greater than 5

Answer explanation

The code checks if x is exactly 5. If true, it logs 'Five'; otherwise, it logs 'Not Five'. Thus, the output depends on the value of x: 'Five' if x is 5, 'Not Five' otherwise.

In a for loop, what are the three main components in the initialization, condition, and increment sections?

• Setup, Check, Update

• Initialization, Condition, Increment

• Start, Test, Finish

• Begin, Evaluate, Modify

Answer explanation

In a for loop, the three main components are Initialization (setting up the loop variable), Condition (the test that determines if the loop continues), and Increment (updating the loop variable). Thus, the correct answer is 'Initialization, Condition, Increment'.

What is the purpose of a while loop in JavaScript?

• To create a new variable in JavaScript.

• To stop the execution of a program in JavaScript.

• To define a function in JavaScript.

• The purpose of a while loop in JavaScript is to execute a block of code repeatedly as long as a specified condition is true.

Answer explanation

A while loop in JavaScript is used to repeatedly execute a block of code as long as a specified condition remains true, making it essential for tasks that require iteration until a certain condition is met.

Write a simple function declaration that takes two parameters and returns their sum.

• function total(a, b) { return a / b; }

• function addNumbers(x, y) { return x * y; }

• function sum(a, b) { return a - b; }

• function add(a, b) { return a + b; }

Answer explanation

The correct function is 'function add(a, b) { return a + b; }' because it properly takes two parameters and returns their sum. The other options use incorrect operations (division, multiplication, subtraction) instead of addition.

What will happen if the condition in a while loop is never met?

• The while loop will execute indefinitely.

• The while loop will not execute.

• The while loop will execute once.

• The while loop will skip to the next iteration.

Answer explanation

If the condition in a while loop is never met, the loop will not execute at all. This means that the code inside the loop will be skipped, making 'The while loop will not execute' the correct answer.

How can you use a switch statement to handle multiple cases for a single variable?

• You cannot group cases in a switch statement.

• You can only use a switch statement for numeric values.

• You can group cases in a switch statement by listing them consecutively, e.g., case 'value1': case 'value2': // code to execute.

• Each case must have a unique variable name.

Answer explanation

You can group cases in a switch statement by listing them consecutively. This allows you to execute the same code for multiple values, making your code cleaner and more efficient.

What is the output of the following code? let i = 0; while (i < 3) { console.log(i); i++; }

• -1

• 0 1 2

• 1.5

• 3

Answer explanation

The code initializes i to 0 and enters a loop that runs while i is less than 3. It logs the value of i (0, 1, 2) to the console and increments i each time. The loop stops when i reaches 3, hence the output is 0, 1, 2.