JavaScript Basic Syntax

Variables

// Using var (old way)
var name = "John";

// Using let (block-scoped)
let age = 30;

// Using const (constant value)
const isStudent = true;
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Data Types

Note: Some of the types are not included.

// String
let name = "John";

// Number
let age = 25;

// Boolean
let isStudent = true;

// Undefined
let undefinedValue;

// Null
let emptyValue = null;

// Object
let person = {
  firstName: "Jane",
  lastName: "Doe"
};

// Array
let colors = ["red", "green", "blue"];
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Operators

// Arithmetic Operators
let sum = 10 + 5;        // Addition
let difference = 10 - 5; // Subtraction
let product = 10 * 5;    // Multiplication
let quotient = 10 / 5;   // Division
let remainder = 10 % 3;  // Modulus

// Assignment Operators
let x = 10;
x += 5; // x = x + 5;

// Comparison Operators
let isEqual = (10 == "10");    // true (loose equality)
let isStrictEqual = (10 === 10); // true (strict equality)
let isNotEqual = (10 != 5);    // true
let isGreater = (10 > 5);      // true

// Logical Operators
let and = true && false; // false
let or = true || false;  // true
let not = !true;         // false
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Conditionals

let age = 18;

if (age < 18) {
  console.log("You are a minor.");
} else if (age >= 18 && age < 65) {
  console.log("You are an adult.");
} else {
  console.log("You are a senior citizen.");
}

// Ternary Operator
let canVote = (age >= 18) ? "Yes" : "No";
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Loops

// For Loop
for (let i = 0; i < 5; i++) {
  console.log("Iteration:", i);
}

// While Loop
let i = 0;
while (i < 5) {
  console.log("While Iteration:", i);
  i++;
}

// Do-While Loop
let j = 0;
do {
  console.log("Do-While Iteration:", j);
  j++;
} while (j < 5);
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Functions

// Function Declaration
function greet(name) {
  return "Hello, " + name + "!";
}

console.log(greet("John"));

// Function Expression
const add = function(x, y) {
  return x + y;
};

console.log(add(5, 10));

// Arrow Function (ES6)
const multiply = (x, y) => x * y;

console.log(multiply(3, 4));
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Objects

let car = {
  make: "Toyota",
  model: "Corolla",
  year: 2020,
  start: function() {
    console.log("Car started.");
  }
};

console.log(car.make); // Accessing property
car.start(); // Calling method
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Arrays

let fruits = ["apple", "banana", "cherry"];

console.log(fruits[0]); // Accessing array elements

fruits.push("orange");  // Adding an element to the array

fruits.pop();           // Removing the last element from the array

console.log(fruits.length); // Getting the length of the array
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String Methods

let text = "Hello, World!";

console.log(text.length);       // Length of the string
console.log(text.toUpperCase()); // Convert to uppercase
console.log(text.toLowerCase()); // Convert to lowercase
console.log(text.indexOf("World")); // Find the position of a substring
console.log(text.slice(0, 5));   // Extract a part of the string
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Array Methods

let numbers = [1, 2, 3, 4, 5];

let doubled = numbers.map(function(num) {
  return num * 2;
});

console.log(doubled); // [2, 4, 6, 8, 10]

let evenNumbers = numbers.filter(function(num) {
  return num % 2 === 0;
});

console.log(evenNumbers); // [2, 4]

let sum = numbers.reduce(function(total, num) {
  return total + num;
}, 0);

console.log(sum); // 15
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Events

document.getElementById("myButton").addEventListener("click", function() {
  alert("Button was clicked!");
});
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Error Handling

try {
  let result = someFunction();
  console.log(result);
} catch (error) {
  console.error("An error occurred:", error.message);
} finally {
  console.log("This will always run.");
}
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JSON (JavaScript Object Notation)

let jsonString = '{"name": "John", "age": 30, "city": "New York"}';

let jsonObject = JSON.parse(jsonString); // Convert JSON string to JavaScript object

console.log(jsonObject.name); // Accessing the object property

let newJsonString = JSON.stringify(jsonObject); // Convert JavaScript object to JSON string

console.log(newJsonString);
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Simple Problem Examples

1. Sum of Two Numbers

Problem: Write a function that takes two numbers and returns their sum.

function sum(a, b) {
  return a + b;
}

console.log(sum(3, 4)); // Output: 7
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2. Check if a Number is Even or Odd

Problem: Write a function that checks if a number is even or odd.

function isEven(num) {
  return num % 2 === 0;
}

console.log(isEven(4)); // Output: true
console.log(isEven(7)); // Output: false
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3. Find the Largest Number in an Array

Problem: Write a function that returns the largest number in an array.

function findLargest(arr) {
  return Math.max(...arr);
}

console.log(findLargest([1, 5, 3, 9, 2])); // Output: 9
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4. Reverse a String

Problem: Write a function that reverses a given string.

function reverseString(str) {
  return str.split('').reverse().join('');
}

console.log(reverseString("hello")); // Output: "olleh"
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5. Factorial of a Number

Problem: Write a function that calculates the factorial of a number.

function factorial(n) {
  if (n === 0 || n === 1) {
    return 1;
  }
  return n * factorial(n - 1);
}

console.log(factorial(5)); // Output: 120
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6. Check if a String is a Palindrome

Problem: Write a function that checks if a string is a palindrome.

function isPalindrome(str) {
  let reversed = str.split('').reverse().join('');
  return str === reversed;
}

console.log(isPalindrome("madam")); // Output: true
console.log(isPalindrome("hello")); // Output: false
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7. FizzBuzz

Problem: Write a function that prints numbers from 1 to 100. For multiples of 3, print “Fizz” instead of the number, and for multiples of 5, print “Buzz”. For numbers that are multiples of both 3 and 5, print “FizzBuzz”.

function fizzBuzz() {
  for (let i = 1; i <= 100; i++) {
    if (i % 3 === 0 && i % 5 === 0) {
      console.log("FizzBuzz");
    } else if (i % 3 === 0) {
      console.log("Fizz");
    } else if (i % 5 === 0) {
      console.log("Buzz");
    } else {
      console.log(i);
    }
  }
}

fizzBuzz();
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8. Find the Sum of an Array

Problem: Write a function that returns the sum of all numbers in an array.

function sumArray(arr) {
  return arr.reduce((total, num) => total + num, 0);
}

console.log(sumArray([1, 2, 3, 4, 5])); // Output: 15
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9. Count Vowels in a String

Problem: Write a function that counts the number of vowels in a given string.

function countVowels(str) {
  let count = 0;
  const vowels = "aeiouAEIOU";
  for (let char of str) {
    if (vowels.includes(char)) {
      count++;
    }
  }
  return count;
}

console.log(countVowels("hello")); // Output: 2
console.log(countVowels("javascript")); // Output: 3
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10. Generate a Random Number

Problem: Write a function that generates a random number between two given numbers.

function randomInRange(min, max) {
  return Math.floor(Math.random() * (max - min + 1)) + min;
}

console.log(randomInRange(1, 10)); // Output: a random number between 1 and 10
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These problems are great for practicing basic JavaScript concepts like functions, loops, conditionals, and array manipulation.

Concepts

Front-End Web Development Concepts

HTML (Hypertext Markup Language): The standard language for creating web pages, defining the structure of content.

CSS (Cascading Style Sheets): Used to style and layout web pages, including colors, fonts, and spacing.

JavaScript: A programming language used to add interactivity to web pages, such as animations and form validation.

Responsive Design: An approach to web design that ensures websites work well on a variety of devices and screen sizes.

DOM (Document Object Model): A programming interface that allows scripts to update the content, structure, and style of a document dynamically.

AJAX (Asynchronous JavaScript and XML): A technique for creating faster and more dynamic web pages by updating parts of a web page without reloading the whole page.

Single Page Application (SPA): A web application that interacts with the user by dynamically rewriting the current page, rather than loading entire new pages from the server.

Progressive Web Apps (PWA): Web applications that use modern web capabilities to deliver an app-like experience to users.

Bootstrap: A popular front-end framework for developing responsive and mobile-first websites.

SASS/LESS: CSS preprocessors that allow you to use variables, nested rules, and functions in your CSS.

Client-Side Rendering (CSR): Rendering web content in the browser using JavaScript, often used in single-page applications.

Cross-Browser Compatibility: Ensuring that a website works consistently across different web browsers.

Web Accessibility: The practice of making websites usable by people of all abilities and disabilities.

UX/UI Design (User Experience/User Interface): The process of enhancing user satisfaction by improving the usability, accessibility, and aesthetics of a website.

Back-End Web Development Concepts

Server: A system that provides data, services, or resources to other computers, known as clients, over a network.

Database: Organized collection of data that is stored and accessed electronically, often used in the back-end of websites.

SQL (Structured Query Language): A language used to manage and manipulate databases.

NoSQL: A type of database that provides a mechanism for storage and retrieval of data modeled in means other than tabular relations (used in SQL databases).

API (Application Programming Interface): A set of rules and tools that allows different software applications to communicate with each other.

RESTful Services: Web services that adhere to the REST (Representational State Transfer) architecture, using HTTP requests to access and use data.

GraphQL: A query language for your API, providing a more efficient, powerful, and flexible alternative to REST.

MVC (Model-View-Controller): A design pattern used in software engineering to separate the application logic, user interface, and control flow.

Authentication: The process of verifying the identity of a user or process.

Authorization: The process of granting or denying a user’s access to resources.

JWT (JSON Web Token): A compact, URL-safe means of representing claims to be transferred between two parties, often used for authorization.

OAuth: An open standard for access delegation commonly used for token-based authentication.

Session Management: Managing user sessions on the server, including how long they last and how they are terminated.

Cookies: Small pieces of data stored on the user’s browser that help websites remember information about the user.

Session Storage/Local Storage: Web storage mechanisms that allow websites to store data locally within the user’s browser.

Caching: The process of storing data temporarily to speed up future access.

Load Balancing: Distributing network or application traffic across multiple servers to ensure reliability and performance.

Database Indexing: A data structure that improves the speed of data retrieval operations on a database table.

ORM (Object-Relational Mapping): A technique for converting data between incompatible type systems using object-oriented programming languages.

SQL Injection: A code injection technique that might destroy your database, one of the most common web hacking techniques.

Web Security: Practices and tools used to protect web applications from threats like hacking, data breaches, and viruses.

SSL/TLS (Secure Sockets Layer/Transport Layer Security): Protocols that encrypt data transferred over the internet, securing communication between web browsers and servers.

WebSocket: A protocol that enables real-time, two-way communication between a client and server.

Microservices: An architectural style that structures an application as a collection of loosely coupled services.

Containerization (Docker): A lightweight form of virtualization that packages an application and its dependencies into a container.

Continuous Integration/Continuous Deployment (CI/CD): Practices that involve automatically testing and deploying code changes to ensure faster, more reliable software delivery.

Reverse Proxy: A server that sits in front of web servers and forwards client requests to those servers.

Content Delivery Network (CDN): A network of servers that delivers web content to users based on their geographic location, improving load times.

Web Server: Software that serves web pages to users by processing incoming requests and delivering content.

Application Server: A server that provides business logic and manages application operations between users and back-end databases.

Middleware: Software that connects different components of an application, allowing them to communicate and manage data.

Logs/Monitoring: The process of recording, analyzing, and responding to the operational data generated by applications and servers.

Queues (e.g., RabbitMQ, Kafka): A system that manages tasks or messages between distributed services or applications.

Web Frameworks: Tools and libraries designed to help streamline the development process (e.g., Django for Python, Laravel for PHP).

Database Migration: The process of transferring data between storage types, formats, or systems.

Cloud Computing: The delivery of computing services (servers, storage, databases, networking, software) over the cloud.

Load Testing: The process of putting demand on a system and measuring its response to ensure it can handle expected loads.

Scalability: The ability of a system to handle increased load by adding resources.

Server-Side Rendering (SSR): A technique for rendering web pages on the server rather than in the browser, improving load times and SEO.

Environment Variables: Variables that are defined outside of the application code and are used to configure the environment in which the application runs.

Version Control (e.g., Git): A system that records changes to files over time, allowing developers to track history and collaborate on projects.

General Technical Vocabulary

• Access
• Account
• Action
• Activate
• Add
• Admin
• Advanced
• Algorithm
• Analyze
• API (Application Programming Interface)
• Application
• Array
• Assign
• Asynchronous
• Attribute
• Authentication
• Authorization
• Backup
• Binary
• Boolean
• Breakpoint
• Browser
• Buffer
• Bug
• Build
• Cache
• Callback
• Certificate
• Character
• Class
• Client
• Code
• Compile
• Component
• Configuration
• Connect
• Console
• Constant
• Constructor
• Container
• Context
• Control
• Convert
• Cookie
• Credentials
• Cryptography
• CSS (Cascading Style Sheets)
• Data
• Database
• Debug
• Default
• Deploy
• Dependency
• Design
• Desktop
• Device
• Development
• Directory
• Document
• Domain
• Download
• Element
• Email
• Encode
• Encryption
• Endpoint
• Environment
• Error
• Execute
• Export
• Extension
• Feature
• File
• Firewall
• Flag
• Font
• Framework
• Function
• Gateway
• Git
• Header
• Host
• HTML (Hypertext Markup Language)
• HTTP/HTTPS (Hypertext Transfer Protocol/Secure)
• Identifier
• Import
• Index
• Input
• Instance
• Interface
• Internet
• IP Address
• JavaScript
• Kernel
• Key
• Language
• Library
• Link
• Load
• Log
• Loop
• Machine
• Memory
• Method
• Mobile
• Module
• Network
• Node
• Notification
• Object
• Open Source
• Operator
• Option
• Output
• Package
• Parameter
• Parse
• Password
• Path
• Permission
• Pixel
• Platform
• Plugin
• Port
• Process
• Program
• Protocol
• Proxy
• Query
• Queue
• Record
• Redirect
• Refactor
• Register
• Repository
• Request
• Resource
• Response
• Restore
• Return
• Route
• Runtime
• Script
• Search
• Security
• Select
• Server
• Service
• Session
• Setting
• Shell
• Signal
• Socket
• Source
• Stack
• Storage
• String
• Structure
• Submit
• Syntax
• System
• Tag
• Template
• Terminal
• Thread
• Token
• Tool
• Traffic
• Transaction
• Transfer
• Trigger
• Type
• UI/UX (User Interface/User Experience)
• Update
• Upload
• User
• Validate
• Value
• Variable
• Version
• Virtual
• Visual
• Web
• Website
• Widget
• Window
• Wireframe
• Workflow
• Programming-Specific Vocabulary
• Abstract
• Argument
• Array
• Assign
• Boolean
• Class
• Closure
• Command
• Compile
• Conditional
• Constructor
• Data Type
• Debug
• Declaration
• Definition
• Delegate
• Dependency
• Enumeration
• Event
• Exception
• Expression
• Framework
• Function
• Inheritance
• Instance
• Interface
• Iteration
• Lambda
• Library
• Literal
• Loop
• Method
• Namespace
• Object
• Operator
• Overload
• Parameter
• Polymorphism
• Procedure
• Property
• Protocol
• Recursion
• Return
• Scope
• Sequence
• Statement
• Syntax
• Thread
• Tuple
• Type
• Variable
• Web Development Vocabulary
• AJAX (Asynchronous JavaScript and XML)
• Anchor
• Attribute
• Backend
• Base URL
• Block Element
• Bootstrap
• Browser Compatibility
• Cache-Control
• Cascading
• CDN (Content Delivery Network)
• Charset
• Class Selector
• Client-Side
• CMS (Content Management System)
• Cross-Origin
• CSS Grid
• DOM (Document Object Model)
• DOCTYPE
• Element Selector
• Emmet
• Favicon
• Flexbox
• Font-Family
• Frontend
• Grid System
• Header Tag
• ID Selector
• Inline Element
• JQuery
• Media Query
• Meta Tag
• Modal
• Navigation Bar
• Padding
• Positioning
• Pseudo-Class
• Responsive Design
• Selector
• Server-Side
• Session Storage
• SPA (Single Page Application)
• Styling
• Tag
• UI Components
• Viewport
• WebSocket
• Wrapper
• Cloud and DevOps Vocabulary
• API Gateway
• CI/CD (Continuous Integration/Continuous Deployment)
• Cloud Computing
• Cluster
• Containerization
• Deployment
• DevOps
• DNS (Domain Name System)
• Environment Variable
• Infrastructure
• Instance
• Kubernetes
• Load Balancer
• Microservices
• Provisioning
• Scalability
• Service Mesh
• Serverless
• Terraform
• Virtual Machine (VM)
• Security Vocabulary
• Authentication
• Authorization
• Backdoor
• Brute Force
• CORS (Cross-Origin Resource Sharing)
• CSRF (Cross-Site Request Forgery)
• Encryption
• Firewall
• Hashing
• HTTPS
• Injection
• Malware
• Phishing
• RSA (Rivest-Shamir-Adleman)
• SSL/TLS
• Token
• Vulnerability
• Zero-Day

Phrases

• Access: “You need to request access to the database before you can retrieve any data.”
• Account: “Create an account to access the premium features of the application.”
• Activate: “Activate your account by clicking on the link sent to your email.”
• Add: “Add the new user to the system by filling out the registration form.”
• Admin: “The admin panel allows you to manage users and settings.”
• Advanced: “This advanced course covers complex algorithms and data structures.”
• Algorithm: “The algorithm sorts the data in ascending order.”
• Analyze: “Analyze the log files to identify any errors in the system.”
• API (Application Programming Interface): “The API allows developers to interact with the service programmatically.”
• Application: “This web application is built using React and Node.js.”
• Array: “Store the list of items in an array for easy access and manipulation.”
• Assign: “Assign a value to the variable before using it in the function.”
• Asynchronous: “Asynchronous operations allow the program to continue running while waiting for a task to complete.”
• Attribute: “The src attribute in the img tag specifies the path to the image.”
• Authentication: “Authentication is required to access secure areas of the website.”
• Authorization: “Authorization determines what resources a user can access after authentication.”
• Backup: “Make sure to backup your data regularly to prevent loss.”
• Binary: “Data is stored in binary format on the disk.”
• Boolean: “A boolean value can be either true or false.”
• Breakpoint: “Set a breakpoint in the code to pause execution and inspect variables.”
• Browser: “The website is optimized for all major browsers.”
• Buffer: “The buffer temporarily holds data before it’s processed.”
• Bug: “There’s a bug in the code that causes the application to crash.”
• Build: “Build the project before deploying it to the server.”
• Cache: “Clearing the cache can help resolve loading issues in your browser.”
• Callback: “Use a callback function to execute code after an asynchronous operation completes.”
• Certificate: “The SSL certificate ensures secure communication between the client and server.”
• Character: “The string contains 20 characters, including spaces.”
• Class: “Define a class in the code to represent objects with common properties.”
• Client: “The client sends a request to the server to retrieve data.”
• Code: “Write clean and efficient code to improve the application’s performance.”
• Compile: “Compile the code to check for syntax errors before running it.”
• Component: “Each component in a React application manages its own state.”
• Configuration: “Update the configuration file to change the database connection settings.”
• Connect: “Connect to the database using the provided credentials.”
• Console: “The console displays error messages and logs during development.”
• Constant: “Declare a constant for values that should not change.”
• Constructor: “The constructor function initializes the object’s properties.”
• Container: “Containers allow you to run applications in isolated environments.”
• Context: “The context provides information about the current state of the application.”
• Control: “Use control statements like if and switch to manage the flow of the program.”
• Convert: “Convert the data type from string to integer before performing calculations.”
• Cookie: “Cookies store user preferences and session information.”
• Credentials: “Enter your credentials to log in to the system.”
• Cryptography: “Cryptography is used to secure data by encrypting it.”
• CSS (Cascading Style Sheets): “Use CSS to style the appearance of your website.”
• Data: “The data is stored in a relational database for easy access.”
• Database: “The database holds all the user information and transaction records.”
• Debug: “Debug the code to find and fix errors.”
• Default: “The default value is used if no input is provided by the user.”
• Deploy: “Deploy the application to the production server after testing.”
• Dependency: “The project has several dependencies that need to be installed.”
• Design: “The design phase involves creating wireframes and mockups.”
• Desktop: “This application is available for both desktop and mobile platforms.”
• Device: “Ensure the website is responsive on all devices.”
• Development: “The development environment is where you write and test your code.”
• Directory: “Navigate to the project directory to access the source files.”
• Document: “The HTML document is structured with various tags and elements.”
• Domain: “Register a domain name for your website.”
• Download: “Download the latest version of the software from the official website.”
• Element: “Each HTML element represents a different part of the web page.”
• Email: “Use a valid email address to sign up for the newsletter.”
• Encode: “Encode the data before sending it over the network.”
• Encryption: “Encryption ensures that data is secure during transmission.”
• Endpoint: “The API endpoint is where the client sends requests to the server.”
• Environment: “Set up the development environment before starting the project.”
• Error: “An error occurred while processing your request.”
• Execute: “Execute the script to run the program.”
• Export: “Export the data to a CSV file for analysis.”
• Extension: “Install a browser extension to enhance functionality.”
• Feature: “This new feature allows users to share content directly from the app.”
• File: “Save the file with a .txt extension.”
• Firewall: “The firewall protects the network from unauthorized access.”
• Flag: “Use a flag to indicate whether the operation was successful.”
• Font: “Choose a readable font for the website’s text.”
• Framework: “React is a popular JavaScript framework for building user interfaces.”
• Function: “Call the function to perform a specific task in the program.”
• Gateway: “The gateway manages the flow of data between networks.”
• Git: “Use Git to track changes in your code repository.”
• Header: “The HTTP header contains metadata about the request.”
• Host: “The website is hosted on a cloud server.”
• HTML (Hypertext Markup Language): “HTML is the standard language for creating web pages.”
• HTTP/HTTPS (Hypertext Transfer Protocol/Secure): “HTTPS secures the communication between the client and server.”
• Identifier: “Use a unique identifier for each element in the HTML document.”
• Import: “Import the module to use its functions in your code.”
• Index: “The index file is the entry point for the application.”
• Input: “The user input is validated before processing.”
• Instance: “Create an instance of the class to use its methods.”
• Interface: “The user interface should be intuitive and easy to navigate.”
• Internet: “The application requires an internet connection to function properly.”
• IP Address: “The IP address identifies the device on the network.”
• JavaScript: “JavaScript is used to add interactivity to web pages.”
• Kernel: “The kernel is the core component of an operating system.”
• Key: “The key is used to encrypt and decrypt the data.”
• Language: “Python is a popular programming language for data analysis.”
• Library: “Use a JavaScript library like jQuery to simplify DOM manipulation.”
• Link: “Click the link to view more details.”
• Load: “The page takes a few seconds to load all the resources.”
• Log: “Check the log files for any errors during the operation.”
• Loop: “The loop iterates over the array to process each element.”
• Machine: “The virtual machine runs multiple operating systems simultaneously.”
• Memory: “The application consumes a lot of memory during execution.”
• Method: “Call the method to perform an action on the object.”
• Mobile: “The mobile version of the website is optimized for touchscreens.”
• Module: “The module contains reusable functions for the application.”
• Network: “The network connection is required to access the server.”
• Node: “Each node in the DOM tree represents an element in the HTML document.”
• Notification: “The user receives a notification when the download is complete.”
• Object: “Create an object to store data and methods.”
• Open Source: “The software is open source, meaning the source code is freely available.”
• Operator: “Use the + operator to add two numbers.”
• Option: “Select an option from the dropdown menu.”
• Output: “The output of the program is displayed in the console.”
• Package: “Install the package using the package manager.”
• Parameter: “Pass parameters to the function to customize its behavior.”
• Parse: “Parse the JSON data to extract the values.”
• Password: “Enter your password to log in to the