Loops & Iteration plus Conditional Logic

Question 1

What is a conditional statement?

Answer 1

A statement that executes code only if a specific condition is true.

Question 2

What keyword is used for a basic condition?

Answer 2

The if keyword. Example: if (x > 10) { console.log('big'); }

Question 3

How do you add an alternative condition?

Answer 3

Use else if. Example: if (x > 10) {...} else if (x > 5) {...}

Question 4

How do you provide a fallback for when no conditions are true?

Answer 4

Use else. Example: if (...) {...} else {...}

Question 5

What is the ternary operator?

Answer 5

A shorthand for if...else. Example: let msg = age >= 18 ? 'Adult' : 'Minor';

Question 6

How do you compare values strictly?

Answer 6

Use === and !== for strict equality and inequality (compares type and value).

Question 7

What is the difference between == and ===?

Answer 7

== compares values after type conversion; === compares both type and value.

Question 8

How do you check multiple conditions?

Answer 8

Use logical operators && (AND), || (OR), and ! (NOT). Example: if (x > 0 && y > 0)

Question 9

How do you use a switch statement?

Answer 9

Use switch(expression) with case labels. Example: switch(day){ case 'Mon': ... break; }

Question 10

Why is break used in a switch statement?

Answer 10

To prevent fall-through (stops execution of the next case).

Question 11

What does default do in a switch statement?

Answer 11

It defines the code to run if no case matches.

Question 12

What is short-circuit evaluation?

Answer 12

When JavaScript stops evaluating as soon as the result is known. Example: true || false returns true immediately.

Question 13

What is a loop?

Answer 13

A control structure that repeats code until a condition is false.

Question 14

What is a for loop used for?

Answer 14

To run code a specific number of times. Example: for (let i = 0; i < 5; i++) {...}

Question 15

What are the three parts of a for loop?

Answer 15

Initialization, condition, and increment. Example: for (let i=0; i<10; i++)

Question 16

What is a while loop?

Answer 16

Runs code while a condition is true. Example: while (count < 5) {...}

Question 17

What is a do...while loop?

Answer 17

Executes code at least once before checking the condition. Example: do {...} while (x < 5);

Question 18

What does the break statement do in loops?

Answer 18

Immediately exits the loop.

Question 19

What does the continue statement do?

Answer 19

Skips the current iteration and moves to the next one.

Question 20

How do you loop through an array?

Answer 20

Use a for loop or .forEach(). Example: arr.forEach(item => console.log(item));

Question 21

How do you loop through object properties?

Answer 21

Use a for...in loop. Example: for (let key in obj) {...}

Question 22

How do you loop through iterable objects like arrays?

Answer 22

Use a for...of loop. Example: for (let value of arr) {...}

Question 23

What is the difference between for...in and for...of?

Answer 23

for...in iterates over keys (indexes), for...of iterates over values.

Question 24

How do you exit multiple nested loops?

Answer 24

Use labels with break. Example: break outerLoop;

Question 25

How can you iterate with a function instead of a loop?

Answer 25

Use array methods like `.map()`, `.filter()`, or `.reduce()`.

Question 26

What is an infinite loop?

Answer 26

A loop that never ends because the condition always evaluates to true.

Question 27

How can you avoid infinite loops?

Answer 27

Always ensure your loop condition will eventually become false.

Question 28

What does `Array.prototype.forEach()` do?

Answer 28

Executes a callback once for each array element.

Question 29

Can you use `break` in `.forEach()`?

Answer 29

No, `.forEach()` cannot be stopped early; use a regular `for` loop or `.some()` instead.

Question 30

What’s a practical use for loops?

Answer 30

Iterating over data, rendering UI elements, or performing repetitive calculations.

Question 31

What’s a practical use for conditionals?

Answer 31

Making decisions in code — e.g., displaying messages, validating input, or controlling flow.

Question 32

What is nesting in control structures?

Answer 32

Placing one loop or conditional inside another for complex logic. Example: `if(x){ for(...) {...} }`