JavaScript Fundamentals Quiz

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Questions and Answers

What is the purpose of using backticks in JavaScript strings?

To create static strings without dynamic inputs
To reduce the code complexity and allow dynamic inputs (correct)
To enforce strict string formatting rules
To prevent variable interpolation within the string

Which statement correctly describes an anonymous function in JavaScript?

An anonymous function can only be invoked where it is defined. (correct)
An anonymous function can be called multiple times without storing it in a variable.
An anonymous function must have a name for reference.
An anonymous function cannot access its arguments once defined.

Which of the following demonstrates the correct syntax for an anonymous arrow function?

var greet = function() {}
(() => { console.log('Hello'); })() (correct)
const greet = function => {}
function() { console.log('Hello'); }

How many types of loops are primarily used in JavaScript?

Four: for loops, for-in loops, while loops, and do...while loops (A) Signup and view all the answers

What is the result of the following code: document.getElementById('demo').innerHTML = 5 + 6?

11 (D) Signup and view all the answers

Which method can only be used while a document is being parsed?

document.write() (A) Signup and view all the answers

What output will the following code produce: alert(sum); where sum is the result of x + y and x = 10, y = 20?

30 (D) Signup and view all the answers

What type of data is represented by the value: 'Hello World!'?

String (C) Signup and view all the answers

Which of the following methods is primarily used for debugging purposes in JavaScript?

console.log() (C) Signup and view all the answers

What is the correct way to initialize a string variable in JavaScript?

var name = 'John'; (A) Signup and view all the answers

What type of data does the value null represent in JavaScript?

The absence of a value (D) Signup and view all the answers

Which of the following is NOT a data type in JavaScript?

Character (A) Signup and view all the answers

What is the correct way to include an external JavaScript file in an HTML document?

Which of the following statements about client-side and server-side scripting is true?

Client-side scripts are interpreted by the web browser. (D) Signup and view all the answers

In JavaScript, which of the following is true regarding case sensitivity?

Function names must always be typed with consistent capitalization. (C) Signup and view all the answers

What is the output of the following JavaScript code: `var x = 5; var y = 10; var sum = x + y; document.write(sum);`?

15 (D) Signup and view all the answers

How can JavaScript be used in relation to user input in forms?

To check for invalid data entered in form fields. (A) Signup and view all the answers

What is the purpose of the `alert` function in JavaScript?

To display a pop-up message to the user. (D) Signup and view all the answers

Which of the following JavaScript code snippets correctly defines a function?

function sayHello() { alert('Hello!'); } (D) Signup and view all the answers

What type of output can be expected from the following code: `document.write(greet);` when greet is set to 'Hello World!'?

Outputs 'Hello World!' on the web page. (A) Signup and view all the answers

What is the primary function used to convert a JSON string into a JavaScript object?

JSON.parse() (A) Signup and view all the answers

Which of the following statements about JSON and functions is true?

Functions must be converted into strings to be represented in JSON. (A) Signup and view all the answers

What will happen if a JavaScript object containing a function is converted to JSON using JSON.stringify()?

The function will be ignored and not included in the JSON string. (D) Signup and view all the answers

Given the JavaScript code, what is the result of executing `document.getElementById('demo').innerHTML = obj.employees.firstName + ' ' + obj.employees.lastName;`?

It will throw an error because 'employees' is an array. (C) Signup and view all the answers

When receiving data from a web server, how should the string data be processed in JavaScript?

It must be parsed using JSON.parse() to be usable. (C) Signup and view all the answers

In the provided JavaScript code, what does the variable 'obj' represent after executing `var obj = JSON.parse(text);`?

A JavaScript object constructed from the parsed JSON data. (B) Signup and view all the answers

What is the correct way to parse a variable `txt` containing a JSON string?

var obj = JSON.parse(txt); (D) Signup and view all the answers

Which of the following JSON strings is correctly formatted?

{ "name": "John", "age": 30 } (C) Signup and view all the answers

What is the purpose of the 'else if' statement in an if...else if...else structure?

To create an alternative condition if the first condition is false (C) Signup and view all the answers

In a switch...case statement, what happens if none of the cases match the value of the variable?

The block of code under 'default' will be executed (D) Signup and view all the answers

Which of the following statements correctly depicts a JavaScript block statement?

if (x == 5) { console.log(x); } (D) Signup and view all the answers

What will be the output of the following code? var a = 10; { var a = 20; } console.log(a);

20 (D) Signup and view all the answers

What is the role of the 'break' statement in a switch...case statement?

To stop execution of the switch statement and exit (D) Signup and view all the answers

What happens when you declare a variable using 'var' inside a block statement?

The variable is accessible outside the block (C) Signup and view all the answers

Given the JavaScript code, what will be alerted if today is Tuesday (dayOfWeek == 2)? var now = new Date(); var dayOfWeek = now.getDay(); if(dayOfWeek == 5) { alert('Have a nice weekend!'); } else if(dayOfWeek == 0) { alert('Have a nice Sunday!'); } else { alert('Have a nice day!'); }

Have a nice day! (B) Signup and view all the answers

What keyword is used to execute code when a switch case matches?

case (A) Signup and view all the answers

What is the main benefit of using string interpolation in JavaScript?

It simplifies the code by reducing the number of console statements. (B) Signup and view all the answers

How are anonymous functions typically accessed in JavaScript?

By the variable they are assigned to. (B) Signup and view all the answers

Which of the following correctly illustrates the structure of a for loop in JavaScript?

for (let i = 0; i < 10; i++) { console.log(i); } (C) Signup and view all the answers

What is a limitation of using anonymous functions in JavaScript?

They cannot be reused once defined. (A) Signup and view all the answers

Which of the following statements about the do...while loop is correct?

It runs the block of code at least once before checking the condition. (D) Signup and view all the answers

What is true about the use of the function keyword in an anonymous function?

The function keyword is used without the function name. (C) Signup and view all the answers

Why might one prefer to use an anonymous function over a named function in JavaScript?

To avoid polluting the global scope. (A) Signup and view all the answers

Which type of loop checks its condition after executing its block of code at least once?

do...while loop (B) Signup and view all the answers

Study Notes

Embedding JavaScript

You can add JavaScript code directly within HTML using <script> tags.
JavaScript code can be written in a separate .js file and included using the src attribute in the <script> tag.

Client-Side vs. Server-Side Scripting

Client-side scripting languages (JavaScript, VBScript) execute in the user's web browser.
Server-side scripting languages (PHP, ASP, Java, Python, Ruby) execute on the web server and send HTML to the browser.
Server-side scripts are slower due to remote processing.

JavaScript Syntax

JavaScript programs are made of JavaScript statements.
JavaScript is case-sensitive.
Use document.getElementById(id) to access HTML elements, innerHTML to modify content.

JavaScript Output Methods

document.write( ) writes content to the current document while it's being parsed.
alert ( ) displays a pop-up dialog box to the user.
console.log() displays data in the browser's developer console for debugging purposes.

JavaScript Data Types

String: Used to represent text data enclosed in single or double quotes.
Number: Used for numeric values.
Boolean: Represents truth (true) or falsity (false).
Array: A collection of data items stored in a specific order.
Undefined: Indicates a variable has been declared but not assigned a value.
Null: Represents the intentional absence of a value.
Object: A collection of key-value pairs, used to represent complex data structures.
Function: A block of code that can be executed on demand.

String Interpolation

Use backticks ( ) to create a string where expressions within curly braces ({}) are evaluated and inserted into the string.

Anonymous Functions

Functions without a name.
Declared using the function keyword.
Accessible only through a variable it's stored in.
Can be defined using arrow function syntax: ( () => { // Function Body… } )();.

JavaScript Loops

Loops allow you to repeat code efficiently.
Types of loops:
- for loop: Repeats a block of code as long as a condition is met.
- for...in loop: Iterates through the properties of an object.
- while loop: Repeats a block of code as long as a condition is true.
- do…while loop: Executes a block of code at least once, and then repeats as long as a condition is true.

JavaScript Conditional Statements

if...else if...else Statement: Evaluates conditions in order.
switch...case Statement: Tests a variable against multiple values and executes the corresponding block of code.
break Statement: Used to exit a loop or switch statement.

JavaScript Block Statements

Block statements group zero or more statements.
Used to create scopes for variables declared using var.

JSON.parse( )

Used to convert a JSON string into a JavaScript object.
Allows easy access to data within the object.

JSON.stringify( )

Converts a JavaScript object into a JSON string.
Removes functions from the object.

Parsing Functions in JSON

Functions are not allowed in JSON.
Convert functions to strings before using JSON.stringify().
Use eval( ) to convert the string back into a function.

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Description

Test your knowledge on JavaScript fundamentals including embedding code, differences between client-side and server-side scripting, syntax, and output methods. This quiz will cover key concepts and practical applications of JavaScript in web development.