JavaScript Basics Quiz

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Questions and Answers

What is the correct way to declare a variable named 'myVar' and assign it the value 'Hello World'?

var myVar = 'Hello World';
let myVar = 'Hello World'; (correct)
const myVar = 'Hello World';
variable myVar = 'Hello World';

Which data type is used to represent a value that is true or false?

null
boolean (correct)
string
number

What is the purpose of the `const` keyword in JavaScript?

To declare a variable whose value cannot be changed. (correct)
To define a function.
To create an object.
To declare a variable that can be reassigned.

What is the maximum value that can be represented by the `number` data type in Javascript?

2^53 - 1 (D) Signup and view all the answers

What is the purpose of using a switch statement in JavaScript?

To execute different blocks of code based on the value of a variable. (D) Signup and view all the answers

Which of the following is a valid variable name in JavaScript?

myVariable$ (A), my_variable (D) Signup and view all the answers

Which of the following code snippets correctly rewrites the given code using a single switch statement?

<pre><code class="language-javascript">let a = +prompt('a?', ''); switch (a) { case 0: alert(0); break; case 1: alert(1); break; case 2: alert('2,3'); break; case 3: alert('2,3'); break; } ``` (A) </code></pre> Signup and view all the answers

What is the output of the following code snippet?

Hello, I'm JavaScript! (C) Signup and view all the answers

What is the difference between `null` and `undefined` in Javascript ?

<code>null</code> represents the intentional absence of a value, while <code>undefined</code> represents a variable that has not been assigned a value. (A) Signup and view all the answers

Which of the following is a NOT a valid comment in JavaScript?

(D) Signup and view all the answers

Which of the following is a correct statement about functions in JavaScript?

Functions are used to define the structure and behavior of a JavaScript program. (C) Signup and view all the answers

What is the difference between a local variable and a global variable in JavaScript?

Local variables are declared inside a function, while global variables are declared outside of any function. (A) Signup and view all the answers

What is the difference between `let` and `const` in Javascript?

<code>let</code> is used to declare variables that can be reassigned, while <code>const</code> is used to declare variables that cannot be reassigned. (C) Signup and view all the answers

What will the following code print? `let i = 3; while (i) { alert( i-- ); }`

3, 2, 1 (B) Signup and view all the answers

How can you convert the following code using a `while` loop? `for (let i = 0; i < 3; i++) { alert(` number ${i}! `); }`

<code>let i = 0; while (i < 3) {alert(</code>number ${i}!<code>); i++;}</code> (D) Signup and view all the answers

What is the purpose of the `break` statement in a `switch` statement?

It stops the execution of the entire <code>switch</code> statement. (D) Signup and view all the answers

What output is produced by the following code? `let a = 2 + 2; switch (a) { case 3: alert( 'Too small' ); break; case 4: alert( 'Exactly!' ); break; case 5: alert( 'Too big' ); break; default: alert( "I don't know such values " ); }`

Exactly! (A) Signup and view all the answers

Which of the following code snippets accurately converts the provided switch statement to an equivalent if...else statement?

switch (browser) {
case 'Edge':
alert( "You've got the Edge!" );
break;
case 'Chrome':
case 'Firefox':
case 'Safari':
case 'Opera':
alert( 'Okay we support these browsers too ' );
break;
default:
alert( 'We hope that this page looks ok!' );
}

<pre><code class="language-javascript"> if (browser === 'Edge') { alert( "You've got the Edge!" ); } else if (browser === 'Chrome' || browser === 'Firefox' || browser === 'Safari' || browser === 'Opera') { alert( 'Okay we support these browsers too ' ); } else { alert( 'We hope that this page looks ok!' ); }``` (C) </code></pre> Signup and view all the answers

When writing code to find prime numbers, what is the best way to check if a number is divisible by another number?

Using the modulo operator (%) to check if the remainder is zero. (C) Signup and view all the answers

What is the purpose of the `default` case in a `switch` statement?

It is executed only if none of the preceding <code>case</code> values match the <code>switch</code> expression. (A) Signup and view all the answers

What is the most efficient method to check if a number `n` is prime in a computer program?

Using the <code>Math.sqrt</code> function to check for divisibility by numbers up to the square root of <code>n</code>. (A) Signup and view all the answers

What is the correct implementation of a `while` loop to output prime numbers from 2 to `n`? Assume all necessary variables are declared.

<pre><code class="language-javascript"> while (i <= n) { if (isPrime(i)) { alert(i); } i++; } ``` (C) </code></pre> Signup and view all the answers

What will the output be when executing the code alert(1 && null && 2)?

null (D) Signup and view all the answers

What does the nullish coalescing operator '??' return when both operands are defined?

The first operand (D) Signup and view all the answers

Which part of a for loop can be omitted?

All parts can be omitted (B) Signup and view all the answers

In a while loop, when does the loop typically exit?

When the condition becomes falsy (A) Signup and view all the answers

What is the output of the code alert(alert(1) && alert(2));?

1, 2, and then undefined (C) Signup and view all the answers

What will the following loop output? for (let i = 0; i < 3; i++) { alert(i); }

0, 1, 2 (D) Signup and view all the answers

How does the continue statement affect loop iterations?

It skips to the next iteration (B) Signup and view all the answers

When using a do...while loop, under what condition will the loop execute at least once?

When the condition is initially false (B) Signup and view all the answers

What does JavaScript primarily enable developers to do on web pages?

Implement complex features (A) Signup and view all the answers

Which of the following is true about the ECMA-262 specification?

It provides detailed guidelines on JavaScript language (C) Signup and view all the answers

In which environments can JavaScript execute?

In the browser and on the server (B) Signup and view all the answers

Which JavaScript engine is used in Firefox?

SpiderMonkey (D) Signup and view all the answers

What feature does TypeScript add to JavaScript?

Strict data typing (D) Signup and view all the answers

What file extension is used for a JavaScript file?

.js (B) Signup and view all the answers

How can you run a JavaScript code snippet directly in a web browser?

By opening the Developer Console (A) Signup and view all the answers

What does the command `console.log('Hello World');` do?

Prints 'Hello World' to the console (A) Signup and view all the answers

What is the primary role of statements in JavaScript?

To perform actions and commands (B) Signup and view all the answers

Which of the following is a feature of CoffeeScript?

It introduces a shorter syntax (B) Signup and view all the answers

What will the variable 'age' contain after executing 'let age = prompt("How old are you?", 100);'?

The user input value as a string (B) Signup and view all the answers

What does the confirm function return when the Cancel button is pressed?

false (B) Signup and view all the answers

What type of conversion occurs automatically when using alert with a boolean value?

String conversion (C) Signup and view all the answers

What will the output of 'alert("6" / "2");' be?

3 (B) Signup and view all the answers

What happens to a value of 'null' during numeric conversion?

Becomes 0 (C) Signup and view all the answers

When is explicit conversion necessary?

When converting values for specific computation needs (A) Signup and view all the answers

What is the result of executing 'let value = true; value = String(value);'?

The string "true" (B) Signup and view all the answers

Which of the following statements about string conversion is correct?

Strings can be explicitly converted using String(value) (D) Signup and view all the answers

Flashcards

Number

A data type that represents numbers, including both integers and floating-point numbers.

String

A data type that represents characters, such as letters, numbers, and symbols.