JavaScript Basics

Which of the following best describes the scope of a variable declared with var inside a function?

Which of the following statements about let is true?

Which statement about const is correct?

What does hoisting mean in JavaScript?

What happens if you try to access a let or const variable before its declaration?

Which of the following is a correct rule for naming variables in JavaScript?

Which of the following is a primitive data type in JavaScript?

Which statement correctly describes the BigInt data type in JavaScript?

What value does a variable declared with let hold if it is declared but not explicitly initialized (after its declaration line)?

Which of the following is NOT a valid JavaScript variable name?

Which of the following statements correctly describes the behavior of the var keyword?

Which data type in JavaScript represents the intentional absence of any object value?

Which statement best describes the difference between null and undefined in JavaScript?

What is the output of the following code?

console.log(a); var a = 5;

What is the output of the following code?

console.log(b); let b = 10;

Which statement about hoisting and variable declarations is correct?

Which of the following operations would cause a TypeError due to mixing incompatible types?

What is the primary purpose of using the const keyword in JavaScript?

Which of the following is a correct example of a template literal in JavaScript?

Which of the following statements about type coercion in JavaScript is true?

What is the output of the following code?

console.log(typeof null);

What does the term "temporal dead zone" refer to in JavaScript?

Which operator should you use to ensure that both the value and type are compared in JavaScript?

Which of the following is considered a non-primitive (object) in JavaScript?

What happens if you try to re-declare a variable using let in the same block?

What is the output of the following code?

console.log("5" + 2);

What is the output of the following code?

console.log("5" - 2);

What is the output of the following code?

console.log(0 == false);

What is the output of the following code?

console.log(0 === false);

Which expression correctly ensures that addition happens before multiplication?

What is the primary purpose of using parentheses when calling a function in JavaScript?

Which of the following correctly uses parentheses to wrap a condition in an if statement?

Which construct creates a new variable scope in JavaScript when used with let or const?

How can you distinguish between an object literal and a code block when using curly braces?

What does the following code do?

let numbers = [1, 2, 3, 4];

How do you access the third element in the array let items = ['a', 'b', 'c', 'd'];?

Which of the following is a limitation of using parentheses ( ) in JavaScript?

When you see the following syntax, what is being created?

let userArray = [{ name: "John", age: 30 }];

What is the role of curly braces in the following if statement?

if (x > 0) { let message = "Positive"; console.log(message); }

Which of the following is an example of implicit type coercion in JavaScript?

Implicit type coercion occurs automatically without explicit instructions from the programmer.

In JavaScript, the === operator checks for both _____ and _____, preventing implicit coercion.

What happens when you run the following JavaScript code?

console.log("6" - 2);

Strongly typed languages like Java and C++ allow implicit coercion between numbers and strings.

In JavaScript, using the + operator between a number and a string results in _____, while using -, *, or / usually results in _____.

Which of the following operations will result in implicit type coercion in JavaScript?

In JavaScript, Number("123") is an example of implicit type coercion.

The process of manually converting a value from one type to another is called _____.

What will the following JavaScript code output?

console.log(10 + true);

Primitive types are stored by reference in memory.

Which of the following are primitive types in JavaScript?

Primitive types are ________, meaning they cannot be changed once created.

Non-primitive types are mutable, meaning their values can be modified without creating a new memory allocation.

Which statement correctly describes primitive vs. non-primitive types?

Data structures provide a way to organize and store data efficiently so that it can be accessed, modified, and managed effectively.

Data structures provide a way to organize and store data so that it can be ________, modified, and managed effectively.

Which of the following best describes one major benefit of choosing an appropriate data structure?

The choice of a data structure does not affect the speed of operations such as search, insertion, and deletion.

Which of the following are the three main types of data structures mentioned in the review?

Linear data structures are also known as ________ data structures because they are organized sequentially.

Which of the following is an example of a non-linear data structure?

Hash-based structures typically store data as key-value pairs and are designed for fast lookup operations.

Key operations on data structures include insertion, deletion, access/traversal, and ________.

Data structures determine how data is stored, accessed, and manipulated.

Which type of collection is organized by indexes?

Structured data is like having a well-organized filing system where every piece of information is stored in a specific ________.

Which of the following is a common use for JSON (JavaScript Object Notation)?

In JSON, keys must always be enclosed in quotes, whereas in JavaScript object literals, quotes are not required for keys.

Which of the following is NOT a valid JSON data type?

The equality operator == in JavaScript performs ________ conversion before comparing two values.

The strict equality operator === compares both the value and the data type of two operands.

The strict equality operator === compares both the ________ and the ________ of two operands.

Which of the following best describes the overall role of data structures?

What is the main advantage of using the strict equality operator (===) over the loose equality operator (==) in JavaScript?

Core to looping is the idea of _____. This means you want to perform the same set of actions many times.

Is the process of going through items one by one (for example, each element in an array).

Conditional termination means that a loop stops executing when a specified condition changes (or when a break is encountered).

When should you use a for loop?

Which loop type is best when the number of iterations is unpredictable and depends on a condition?

Which loop guarantees that the code block will run at least once, even if the condition is false from the start?

When iterating over the keys (property names) of an object in JavaScript, which loop should you use

If you want to iterate directly over the values of an iterable object (like an array or string), which loop is most suitable?

A for loop is best used when you know the number of iterations because it handles initialization, condition, and __________ all together.

A while loop may run zero times if the condition is false initially.

A do...while loop always executes its code block at least once before checking the condition.

The loop stops executing when a specified condition changes or a break is encountered; this is called __________ termination.

Which statement best distinguishes sequences, selections, and loops?

A ______ statement is used to immediately exit a loop before its condition naturally becomes false.

Which loop is best when you know the exact number of iterations you need, such as processing every element in a fixed-size array?

Which loop should you use when you need to guarantee that a code block runs at least once, even if the condition is initially false?

The for...in loop is primarily used to iterate over arrays.

The for...of loop iterates directly over the values of an iterable object, making it ideal for arrays and strings.

A loop stops executing when its condition becomes __________.

In the context of looping, the process of going through each item in a set one by one is called:

A semicolons is required after a statement in JavaScript.

How many statements are present inside the function block?

function genie() { let a, b, c; a = 5; b = 9; c = a + b; }

What will be the alerted result?

let x = 5; x = 7; x = x + x; alert(x);

With the let keyword, you can declare variables with the same name in the same block.

The break statement can be used to exit any block of code, including functions, if statements, and loops.

What is the primary difference between using return and break inside a loop that is inside a function?

In JavaScript, the __________ statement is used to immediately exit a loop or switch statement, while the __________ statement is used to exit a function and optionally return a value.

Using return inside a loop will exit the loop but continue executing any code after the loop in the same function.

Which of the following statements is correct about the break statement?

The return statement cannot be used outside of a function.

Consider the following code:

function testLoop() { for (let i = 0; i < 5; i++) { if (i === 3) { break; } console.log(i); } console.log("Loop ended"); } testLoop();

When a return statement is executed inside a function, it immediately terminates the function's execution and optionally returns __________.

If you want to exit a loop early without stopping the execution of the rest of the function, you should use:

Using break in a switch statement prevents the execution from "falling through" to subsequent cases.