Top 250 JavaScript Interview Questions and Answers 2024

Node.js is a server-side JavaScript runtime environment.

• Node.js is built on top of the V8 JavaScript engine from Google Chrome.

• It allows developers to write server-side code in JavaScript.

• Node.js has a non-blocking I/O model, making it efficient for handling large amounts of data.

• Node.js has a vast library of modules available through npm (Node Package Manager).

JavaScript is a scripting language used to add interactivity to HTML pages.

• JavaScript is embedded in HTML using the

A closure is a function that has access to variables in its outer (enclosing) scope.

• A closure is created when a function is defined inside another function

• The inner function has access to the outer function's variables and parameters

• Closures can be used to create private variables and methods

• Example: function outer() { var x = 10; function inner() { console.log(x); } return inner; } var closure = outer(); closure(); // Output: 10

Styles can be added to HTML elements using JavaScript by manipulating the element's style property.

• Access the element using document.getElementById() or document.querySelector()

• Use the style property to set CSS styles, e.g. element.style.color = 'red'

• Styles can also be set using CSS classes, e.g. element.classList.add('my-class')

Class components are ES6 classes that extend the React.Component class, while functional components are just plain JavaScript functions.

• Class components are more feature-rich and have access to lifecycle methods.

• Functional components are simpler and easier to read and test.

• Class components can have state and use lifecycle methods like componentDidMount and componentDidUpdate.

• Functional components are stateless and do not have lifecycle methods.

• Functional components can be use...read more

Select all div using jQuery

• Use the jQuery selector $('div') to select all div elements

• This will return a jQuery object containing all the selected div elements

• You can then perform operations on the selected div elements using jQuery methods

call(), apply() and bind() are methods used to manipulate the 'this' keyword in JavaScript.

• call() and apply() are used to invoke a function with a specific 'this' context and arguments.

• call() accepts arguments as a comma-separated list, while apply() accepts arguments as an array.

• bind() returns a new function with a specific 'this' context, which can be invoked later with arguments.

• bind() is useful for creating a new function with a fixed 'this' context, such as event handler...read more

JavaScript is a programming language used for web development, while Angular is a JavaScript framework for building web applications.

• JavaScript is a programming language that allows developers to add interactivity and dynamic features to websites.

• Angular is a JavaScript framework that provides a structure for building web applications.

• JavaScript can be used independently to create web functionality, while Angular is built on top of JavaScript and provides additional features ...read more

Java and JavaScript are two different programming languages with different use cases.

• Java is used for building server-side applications, Android apps, and enterprise software.

• JavaScript is used for building interactive web applications and front-end development.

• Java is a compiled language while JavaScript is an interpreted language.

• Java is statically typed while JavaScript is dynamically typed.

• Java code runs on the Java Virtual Machine (JVM) while JavaScript code runs on web ...read more

JavaScript is a programming language used for web development, while Node.js is a runtime environment for executing JavaScript code outside of a web browser.

• JavaScript is primarily used for client-side scripting, while Node.js is used for server-side scripting.

• JavaScript is executed in a web browser, while Node.js is executed on a server.

• Node.js provides additional modules and libraries for server-side development, such as file system access and networking capabilities.

• JavaSc...read more

ECMAScript is a standard, while JavaScript is an implementation of that standard.

• ECMAScript is a specification for scripting languages, while JavaScript is a programming language that implements ECMAScript.

• ECMAScript is maintained by ECMA International, while JavaScript is maintained by the Mozilla Foundation.

• ECMAScript is used as a basis for many other programming languages, while JavaScript is used primarily for web development.

• ECMAScript is updated regularly, while JavaScr...read more

Arrow functions are shorter syntax for writing function expressions. They have lexical 'this' binding.

• Arrow functions do not have their own 'this', 'arguments', 'super', or 'new.target' keywords.

• Arrow functions cannot be used as constructors and do not have a prototype property.

• Arrow functions are anonymous and cannot be named.

• Arrow functions have a shorter syntax compared to normal functions.

• Arrow functions have a lexical 'this' binding, meaning they inherit the 'this' value...read more

ES6 introduces new syntax and features to JavaScript.

• Arrow functions

• Template literals

• Let and const keywords

• Destructuring assignment

• Default parameters

• Rest and spread operators

• Classes

• Modules

Generator functions and symbols in JavaScript. Implementation of const keyword in ES5.

• Generator functions are functions that can be paused and resumed, allowing for lazy evaluation of data.

• Symbols are a new primitive type in ES6 that can be used as unique identifiers.

• To implement const in ES5, we can use Object.defineProperty to create a read-only property on an object.

JavaScript is a dynamic scripting language, while TypeScript is a statically typed superset of JavaScript.

• JavaScript is dynamically typed, while TypeScript is statically typed.

• TypeScript supports type checking at compile time, while JavaScript does not.

• TypeScript allows for the use of interfaces and advanced OOP features, while JavaScript does not.

• TypeScript code needs to be transpiled to JavaScript before it can be executed in a browser.

map returns a new array with modified elements, forEach executes a function for each element in an array.

• map returns a new array, forEach does not

• map modifies the elements of the array, forEach does not

• map returns the same number of elements as the original array, forEach does not necessarily

• forEach is used for side effects, map is used for transformation

Rest and spread operators are used in JavaScript to manipulate arrays and objects.

• Rest operator allows us to represent an indefinite number of arguments as an array.

• Spread operator allows us to spread an array or object into individual elements.

• Rest operator is denoted by three dots (...)

• Spread operator is also denoted by three dots (...) but is used in a different context.

• Rest operator can be used in function parameters and destructuring assignments.

• Spread operator can be us...read more

Spread operator is used to split up array elements or object properties, while rest operator is used to merge multiple elements into an array.

• Spread operator is used to expand elements in an array or object.

• Rest operator is used to gather parameters into an array.

• Spread operator can be used to concatenate arrays or objects.

• Rest operator is used in function parameters to collect arguments into an array.

Let, Const, and Var are used to declare variables in JavaScript with different scoping and reassignment abilities.

• Var has function scope and can be redeclared and reassigned.

• Let has block scope and can be reassigned but not redeclared.

• Const has block scope and cannot be reassigned or redeclared.

Create a tab section using JavaScript

• Use HTML and CSS to create the tab structure

• Use JavaScript to handle the tab functionality

• Add event listeners to the tab elements to switch between tabs

Hosting in JavaScript refers to the process of deploying a website or web application on a server to make it accessible on the internet.

• Hosting allows users to access your website by typing in the domain name in a web browser.

• Common hosting services include shared hosting, VPS hosting, and cloud hosting.

• Examples of popular hosting providers include Bluehost, HostGator, and AWS.

• Hosting also involves managing server resources, security, and performance optimization.

Web workers are JavaScript scripts that run in the background, separate from the main browser thread.

• Web workers allow for parallel execution of tasks, improving performance and responsiveness.

• They can perform computationally intensive tasks without blocking the user interface.

• Web workers communicate with the main thread using message passing.

• Examples of tasks suitable for web workers include data processing, image manipulation, and complex calculations.

JavaScript has several datatypes including string, number, boolean, object, array, null, and undefined.

• String: represents a sequence of characters

• Number: represents numeric values

• Boolean: represents true or false

• Object: represents a collection of key-value pairs

• Array: represents an ordered list of values

• Null: represents the intentional absence of any object value

• Undefined: represents an uninitialized variable

Inner HTML allows dynamic manipulation of HTML content using JavaScript.

• Inner HTML can be used to add, remove or modify HTML elements on a webpage.

• It provides a simple and efficient way to update the content of a webpage without reloading the entire page.

• Inner HTML can also be used to create dynamic user interfaces and interactive web applications.

• However, it is important to sanitize user input to prevent security vulnerabilities such as cross-site scripting (XSS) attacks.

Arrow functions are a concise way to write functions in JavaScript.

• Arrow functions have a shorter syntax compared to regular functions.

• They do not have their own 'this' value.

• They do not have the 'arguments' object.

• They cannot be used as constructors with the 'new' keyword.

• They are commonly used in functional programming and with array methods like 'map' and 'filter'.

async/defer are attributes used in script tags to control the loading and execution of JavaScript files.

• async loads the script asynchronously while the HTML document continues to load

• defer loads the script after the HTML document has finished parsing

• async scripts are executed as soon as they are downloaded, while defer scripts are executed in the order they appear in the HTML document

• async is useful for non-essential scripts that don't affect the page's functionality, while d...read more

JS is JavaScript, a programming language used for web development. React JS is a JavaScript library for building user interfaces.

• JavaScript (JS) is a programming language commonly used for creating interactive effects within web browsers.

• React JS is a JavaScript library developed by Facebook for building user interfaces, specifically for single-page applications.

• React JS allows developers to create reusable UI components that can be easily managed and updated.

AJAX (Asynchronous JavaScript and XML) is a technique used in web development to create asynchronous web applications.

• AJAX allows web pages to be updated asynchronously by exchanging data with a web server behind the scenes.

• It enables web pages to be more responsive and interactive without the need to reload the entire page.

• AJAX uses XMLHttpRequest object to communicate with the server and update the page dynamically.

• Commonly used in web applications for features like auto-co...read more

Event loop is a mechanism in JavaScript that handles asynchronous operations.

• Event loop continuously checks the call stack and the task queue.

• If the call stack is empty, it takes the first task from the queue and pushes it to the call stack.

• The task is executed and the process repeats.

• setTimeout and setInterval functions are examples of asynchronous operations that use event loop.

Normal functions are defined using the function keyword, while arrow functions are defined using the => syntax.

• Normal functions are hoisted, while arrow functions are not hoisted.

• Arrow functions do not have their own 'this' keyword, they inherit it from the parent scope.

• Arrow functions do not have their own 'arguments' object.

• Arrow functions are more concise and have implicit return.

• Arrow functions cannot be used as constructors.

To fetch all input values in javascript, we can use the document.querySelectorAll() method.

• Use document.querySelectorAll() method to select all input elements

• Loop through the selected elements to get their values

• Store the values in an array or object for further use

Yes, it is possible to connect to a database using JavaScript.

• JavaScript can connect to databases using APIs such as Web SQL, IndexedDB, and MongoDB.

• It is also possible to use Node.js to connect to databases using JavaScript.

• However, it is not recommended to connect to a database directly from client-side JavaScript due to security concerns.

JS stands for JavaScript, a programming language used for web development. QP stands for Query Parser, a tool used for parsing and analyzing queries.

• JS is a programming language used for web development.

• QP is a tool used for parsing and analyzing queries.

• JS is used for client-side scripting, while QP is used for query parsing and analysis.

• Examples: JavaScript is used to create interactive web pages, while Query Parser is used in search engines to analyze user queries.

Error handling in JavaScript involves using try-catch blocks, throwing custom errors, and using error objects.

• Use try-catch blocks to catch and handle errors

• Throw custom errors using the throw keyword

• Use error objects like Error, SyntaxError, TypeError, etc. for specific types of errors

Var is function-scoped and can be redeclared, while Let is block-scoped and cannot be redeclared.

• Var can be hoisted to the top of its scope, while Let cannot.

• Var can be declared without being initialized, while Let must be initialized before use.

• Var can cause unexpected behavior in loops, while Let avoids this issue.

• Var can be used to declare global variables, while Let cannot.

• Var can be redeclared within its scope, while Let cannot.

The mostly used design patterns in JavaScript are Module, Observer, Singleton, Factory, and Prototype.

• Module pattern helps to keep the code organized and maintainable.

• Observer pattern is used for event handling and notification.

• Singleton pattern restricts the instantiation of a class to a single instance.

• Factory pattern provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects that will be created.

• Prototype pattern creates ...read more

JS hoisting is a mechanism where variable and function declarations are moved to the top of their scope.

• Variable declarations are hoisted but not their values

• Function declarations are fully hoisted

• Let and const declarations are not hoisted

Capitalize last letter of each word in a string and fetch data from API to display in tabular form using React JS.

• Split the string into an array of words

• Iterate through each word and capitalize the last letter

• Join the words back together to form the modified string

• Use React JS to fetch data from API and display in a tabular form

The 'V8' package in R is used to import and execute JavaScript code.

• Use the 'V8' package in R to import and execute JavaScript code.

• Install the 'V8' package using install.packages('V8').

• Load the 'V8' package using library(V8).

• Use the v8() function to create a new V8 context and execute JavaScript code.

Polyfills are code that allows modern browsers to support features that are not natively supported.

• Polyfills are used to bridge the gap between modern web development and older browsers.

• They provide a way to use new features without worrying about browser compatibility.

• Polyfills can be used for features like CSS Grid, Fetch API, and ES6 syntax.

• They are often included in JavaScript libraries and frameworks like React and Angular.

The DOM (Document Object Model) in JavaScript is a programming interface for web documents. It represents the structure of a document as a tree of objects.

• The DOM is a representation of the HTML elements on a webpage.

• It allows JavaScript to interact with and manipulate the content and structure of a webpage.

• DOM methods like getElementById() and querySelector() are commonly used to access and modify elements on a webpage.

The onbeforeunload method is used to prevent form save.

• Use the onbeforeunload method to display a warning message before leaving the page without saving the form.

• Return a custom message in the method to prompt the user to confirm if they want to leave the page.

• Example: window.onbeforeunload = function() { return 'Are you sure you want to leave this page without saving?'; };

The 'this' keyword in JS refers to the object that is currently executing the code.

• The value of 'this' depends on how a function is called.

• In a method, 'this' refers to the object that the method belongs to.

• In a regular function, 'this' refers to the global object (window in a browser).

• In an event handler, 'this' refers to the element that triggered the event.

• The value of 'this' can be explicitly set using call(), apply(), or bind() methods.

async loads script while page continues to load, defer loads script after page has loaded

• async loads scripts asynchronously while page continues to load

• defer loads scripts after the page has loaded

• async scripts may not execute in order, while defer scripts do

• async scripts may cause rendering issues, while defer scripts do not

IIFE stands for Immediately Invoked Function Expression. It is a JavaScript function that is executed as soon as it is defined.

• IIFE is a way to create a function expression and immediately invoke it.

• It helps in creating a private scope for variables and functions.

• It is commonly used to avoid polluting the global namespace.

• IIFE can be written using different syntaxes like using parentheses, function declaration, or arrow functions.

Currying is a technique of transforming a function that takes multiple arguments into a sequence of functions that each take a single argument.

• Currying is achieved by returning a function that takes the next argument until all arguments are received.

• In JavaScript, currying is often used for partial application of functions.

• The sum function in the example takes one argument and returns a function that takes the next argument until all arguments are received.

• The final function ...read more

To manage conflicting JavaScript on a page, we can use various techniques like namespacing, modularization, and event delegation.

• Use namespacing to encapsulate code and prevent conflicts

• Modularize code into smaller, reusable components

• Use event delegation to handle events on dynamically loaded elements

• Avoid global variables and use local scopes

• Use a JavaScript module bundler like Webpack to manage dependencies

Javascript is a scripting language used for web development. It can be used with Core PHP to add interactivity to websites.

• Javascript is a client-side scripting language that runs in the browser

• It can be used to add interactivity to websites, such as form validation and dynamic content

• Core PHP is a server-side scripting language used to generate HTML pages

• Javascript can be used with Core PHP to create dynamic web pages

• For example, you can use Javascript to create a form that ...read more

Yes, I have experience with SQL and JavaScript.

• I have strong SQL skills, including writing complex queries and stored procedures.

• I am proficient in JavaScript for front-end development and have experience with frameworks like React and Angular.

• I have used SQL databases like MySQL and PostgreSQL, as well as NoSQL databases like MongoDB.

• I have developed web applications that interact with databases using SQL and JavaScript.

To connect to MongoDB using Javascript, you can use the official MongoDB Node.js driver.

• Install the MongoDB Node.js driver using npm: npm install mongodb

• Require the MongoDB Node.js driver in your Javascript file: const MongoClient = require('mongodb').MongoClient

• Connect to MongoDB using MongoClient.connect() method

• Specify the MongoDB connection URL and database name in the connect() method

• Access the MongoDB database and perform operations like insert, update, delete, and find

Microservices in JavaScript are small, independent, and loosely coupled services that work together to form a larger application.

• Microservices are designed to be modular and scalable

• Each microservice performs a specific task and communicates with other microservices through APIs

• They can be written in different programming languages and can run on different servers

• Examples of microservices in JavaScript include Netflix, PayPal, and Uber

Bind creates a new function with a specified 'this' value and arguments.

• Bind returns a new function with the same body as the original function.

• The 'this' value of the new function is bound to the first argument passed to bind().

• The subsequent arguments are passed as arguments to the new function.

• Polyfill for bind() can be created using call() or apply() methods.

let is mutable and can be reassigned, const is immutable and cannot be reassigned

• let allows reassignment of values, const does not

• const must be initialized with a value, let can be declared without a value

• const is block-scoped, let is function-scoped

Multithreading is not natively supported in JavaScript, but can be achieved through Web Workers.

• JavaScript is a single-threaded language, meaning it can only execute one task at a time.

• Web Workers allow for multithreading in JavaScript by running scripts in the background.

• Web Workers can communicate with the main thread using message passing.

• Examples of tasks that can benefit from multithreading include heavy computations and long-running processes.

NodeJS is a runtime environment for executing JavaScript code outside of a web browser.

• NodeJS allows JavaScript to be run on the server-side, enabling backend development.

• NodeJS has a built-in library of modules that can be easily integrated into applications.

• NodeJS is event-driven and non-blocking, making it efficient for handling multiple requests simultaneously.

Performance in React JS can be improved by optimizing rendering, reducing unnecessary re-renders, using virtualization, code splitting, and lazy loading.

• Optimize rendering by using shouldComponentUpdate or React.memo

• Reduce unnecessary re-renders by using PureComponent or memoization techniques

• Use virtualization for long lists or tables to improve rendering performance

• Implement code splitting to load only necessary code for each route or component

• Utilize lazy loading to defer ...read more

React is a JavaScript library for building user interfaces. State is data that can change over time within a component. Props are read-only data passed from a parent component. API stands for Application Programming Interface.

• React is a JavaScript library for building user interfaces

• State is data that can change over time within a component

• Props are read-only data passed from a parent component

• API stands for Application Programming Interface

Sets in JavaScript are used to store unique values of any type.

• Create a new set using the Set constructor

• Add values to the set using the add() method

• Check if a value exists in the set using the has() method

• Remove a value from the set using the delete() method

• Iterate over the set using the forEach() method

Exceptions in JavaScript can be handled using try-catch blocks.

• Use try-catch blocks to catch and handle exceptions in JavaScript.

• The try block contains the code that may throw an exception.

• The catch block is used to handle the exception if one occurs.

• You can also use the finally block to execute code after try and catch regardless of the result.

Modules in JavaScript are reusable pieces of code that can be exported from one file and imported into another.

• Modules help in organizing code into separate files for better maintainability.

• Modules can be imported using 'import' keyword and exported using 'export' keyword.

• Modules can be used to encapsulate code and prevent global namespace pollution.

• CommonJS and ES6 modules are two popular module systems in JavaScript.

Recreating tic tac toe game in plain JavaScript

• Create a 3x3 grid using HTML and CSS

• Use JavaScript to handle player turns and check for win conditions

• Implement a reset button to start a new game

Concurrency in JS allows multiple tasks to run simultaneously by utilizing event loop and callback functions.

• JS is single-threaded, meaning it can only execute one task at a time.

• Concurrency is achieved through asynchronous operations using callbacks, promises, and async/await.

• Event loop manages the execution of multiple tasks by queuing them in a stack and executing them one by one.

• Web Workers allow running scripts in background threads to handle heavy computations without b...read more

The @track decorator in Salesforce is used to track changes to a property in a Lightning web component.

• Used to make a property reactive and trigger re-renders when its value changes

• Not mandatory but recommended for properties that need to be reactive

• Use @track when you want changes to a property to be reflected in the UI

Use the WebSocket API in JavaScript to connect to a server socket

• Use the WebSocket constructor to create a new WebSocket object

• Pass the server URL as the first argument to the WebSocket constructor

• Handle the WebSocket events like onopen, onmessage, onerror, and onclose

Scopes in JavaScript determine the accessibility of variables and functions.

• Global scope: variables and functions declared outside any function are accessible globally

• Local scope: variables and functions declared inside a function are only accessible within that function

• Block scope: variables declared with let and const are only accessible within the block they are declared in

• Function scope: variables declared with var are accessible within the function they are declared in

Polyfills are code that provide modern functionality on older browsers that do not natively support it.

• Polyfills are used to fill in the gaps for browser compatibility by replicating the functionality that is missing in older browsers.

• They are typically used for adding support for new ECMAScript features, HTML5 APIs, or CSS properties.

• Examples of polyfills include Babel for ES6 features, fetch polyfill for the Fetch API, and HTML5 Shiv for HTML5 elements in older versions of ...read more

The method used to submit forms in JavaScript is the submit() method.

• The submit() method is called on the form element.

• It can be triggered by a button click or programmatically.

• Example: document.getElementById('myForm').submit();

ASP.NET Core is a cross-platform, high-performance framework for building modern, cloud-based, internet-connected applications.

• Open-source framework developed by Microsoft

• Supports multiple platforms including Windows, macOS, and Linux

• Used for building web applications, APIs, and microservices

• Provides high performance and scalability

• Includes features like dependency injection, middleware, and MVC pattern

forIn loop iterates over the enumerable properties of an object, while forOf loop iterates over the values of an iterable object.

• forIn loop is used for iterating over object properties, while forOf loop is used for iterating over array elements.

• forIn loop can be used with objects, while forOf loop can be used with arrays, strings, maps, sets, etc.

• Example: forIn loop - for (let key in object) { console.log(key); }

• Example: forOf loop - for (let value of array) { console.log(val...read more

JS is a programming language used for web development. Virtual DOM is a concept in React to improve performance.

• JS (JavaScript) is a popular programming language used for web development.

• Virtual DOM is a concept in React where a lightweight copy of the actual DOM is created and updated to improve performance.

• Virtual DOM allows React to efficiently update the actual DOM by only re-rendering components that have changed.

Creating a prototype in JavaScript

• Use the Object.create() method to create a prototype object

• Add properties and methods to the prototype object

• Use the prototype object to create new instances of an object

JS execution happens in two main phases: creation and execution.

• During creation phase, variables are hoisted and memory space is allocated.

• During execution phase, code is executed line by line.

• JS uses a single-threaded, synchronous execution model.

• Functions are first-class citizens in JS, allowing for higher-order functions and closures.

• Event loop and callback queue are used for handling asynchronous operations.

package.json is a configuration file used in Node.js projects to manage dependencies and scripts.

• Contains metadata about the project such as name, version, and author

• Lists dependencies and devDependencies required for the project

• Allows for the creation of custom scripts to run tasks

• Can be used to specify the main file of the project

• Can be generated using 'npm init' command

Use the delay() method in jQuery to add delay for animation.

• Use the delay() method before the animation function.

• Specify the duration of the delay in milliseconds as an argument.

• Example: $(element).delay(1000).fadeOut();

The __proto__ is a property that points to the prototype of an object, while prototype is a property of a constructor function.

• The __proto__ property is used to access the prototype of an object.

• The prototype property is used to add properties and methods to a constructor function.

• The __proto__ property is deprecated and should not be used in production code.

• Changes to the prototype of a constructor function will affect all instances of that constructor function.

Event bubbling is the process where an event triggered on a child element is propagated up through its parent elements.

• Events in JavaScript propagate through the DOM tree from the target element to the root element.

• When an event occurs on a child element, it will also trigger the same event on its parent elements.

• Event bubbling allows for event delegation, where a single event handler is attached to a parent element to manage events for all its children.

Throttling in JavaScript is a technique used to control the rate at which a function is executed.

• Throttling limits the number of times a function can be called over a specified period.

• It is commonly used in scenarios like scroll events, resize events, and API requests to prevent performance issues.

• Example: Debouncing a search input to limit the number of API calls made while typing.

Optional chaining is a feature in JavaScript that allows you to access properties of an object without worrying about whether the object is null or undefined.

• It uses the question mark (?) operator to check if a property exists before accessing it.

• It can be used with both object properties and function calls.

• It can be chained multiple times to access nested properties.

• It was introduced in ECMAScript 2020.

Higher order functions in JavaScript are functions that can take other functions as arguments or return functions as output.

• Higher order functions can be used to create more flexible and reusable code.

• Examples include functions like map, filter, and reduce in JavaScript.

• They allow for functions to be passed as parameters, making code more concise and readable.

JSX is a syntax extension for JavaScript that allows you to write HTML-like code in your JavaScript files.

• JSX stands for JavaScript XML

• It is commonly used with React to define the structure and appearance of components

• JSX elements are transpiled into regular JavaScript function calls

• It allows you to write HTML-like code with JavaScript expressions embedded within curly braces

• Example:

  Hello, {name}!

setTimeout() is a function in JavaScript that allows you to delay the execution of a function for a specified amount of time.

• setTimeout() takes two parameters: a function to be executed and a delay time in milliseconds

• The function passed to setTimeout() is executed once after the specified delay

• setTimeout() returns a unique identifier (timeout ID) that can be used to cancel the execution of the function using clearTimeout()

• Example: setTimeout(function() { console.log('Hello, ...read more

Async and Await are keywords used in JavaScript to handle asynchronous operations in a synchronous way.

• Async is used to declare a function as asynchronous, which means it will always return a promise.

• Await is used to pause the execution of a function until a promise is settled (resolved or rejected).

• Async functions can contain one or more await expressions to wait for promises to be resolved.

• Async functions always return a promise, which allows chaining multiple async functio...read more

Email validation in JavaScript involves checking if the input follows the correct email format.

• Use a regular expression to check if the email follows the correct format

• Check for the presence of '@' symbol and at least one '.' after it

• Validate the email using built-in JavaScript functions or libraries like 'validator.js'

JavaScript is a scripting language that runs on the browser to make web pages interactive and dynamic.

• JavaScript code is embedded in HTML and executed by the browser's JavaScript engine.

• It can manipulate the DOM to change content, style, and structure of a webpage.

• JS can handle user interactions like form submissions, button clicks, and animations.

• It can make asynchronous requests to fetch data from servers using AJAX.

• JS can also store data locally in the browser using Web St...read more

A callback in JavaScript is a function passed as an argument to another function, to be executed later.

• Callback functions are commonly used in asynchronous programming.

• They allow for functions to be executed after another function has finished executing.

• Example: setTimeout function in JavaScript takes a callback function as an argument to be executed after a specified time.

Create a Login form with email validation using Vanilla JS.

• Create a form in HTML with input fields for email and password

• Use JavaScript to validate the email input using regular expressions

• Display error messages if the email input is not in the correct format

The .bind() function in jQuery is used to attach an event handler function to one or more elements.

• It allows you to specify the event type and the function to be executed when the event occurs.

• The .bind() function can be used to bind multiple events to the same element.

• It can also be used to pass additional data to the event handler function.

• The .bind() function is deprecated in jQuery version 3.0 and above. It is recommended to use the .on() function instead.

Elements can be created dynamically in JavaScript using document.createElement() method.

• Use document.createElement() method to create a new element

• Set attributes and content for the element using methods like setAttribute() and innerHTML

• Append the newly created element to an existing element in the DOM using appendChild()

let is used to declare a constant while var is used to declare a variable.

• let is immutable while var is mutable

• let can only be assigned once while var can be assigned multiple times

• let is preferred over var for safety and performance reasons

There is no limit to the number of document ready functions that can be used in a js file.

• Multiple document ready functions can be used to ensure that all necessary elements are loaded before executing code.

• Each document ready function should be enclosed in its own set of parentheses.

• It is important to avoid nesting document ready functions within each other.

• Example: $(document).ready(function() { //code }); $(document).ready(function() { //code });

Elements in JavaScript can be created using the document.createElement() method.

• Use document.createElement() method to create a new element

• Specify the type of element to be created (e.g. 'div', 'p', 'span')

• Append the newly created element to an existing element using appendChild() method

Create a todolist using plain javascript

• Create an input field for adding tasks

• Use an array to store the tasks

• Display the tasks in a list on the webpage

• Add functionality to mark tasks as completed or delete them

Regular functions are defined using the function keyword, while arrow functions use the => syntax.

• Arrow functions have a shorter syntax than regular functions.

• Arrow functions do not have their own 'this' keyword.

• Arrow functions cannot be used as constructors.

• Regular functions can be used as methods on objects, while arrow functions cannot.

• Arrow functions are always anonymous, while regular functions can be named or anonymous.

Temporal Dead Zone is a behavior in JavaScript where variables are not accessible before they are declared.

• Temporal Dead Zone occurs when accessing variables before they are declared

• Variables in the Temporal Dead Zone cannot be accessed or assigned

• The Temporal Dead Zone is a result of JavaScript's hoisting behavior

• Example: accessing a variable before it is declared will throw a ReferenceError

clearInterval is a method used to stop the execution of setInterval() method.

• clearInterval() method is used to stop the execution of setInterval() method.

• It takes the ID returned by setInterval() method as a parameter.

• The ID is used to identify the setInterval() method to be stopped.

• Once clearInterval() is called, the setInterval() method stops executing.

Create a form and log input value to console

• Create an HTML form element with input field

• Add an event listener to the form submit event

• Retrieve the input value using JavaScript

• Log the input value to console

Asynchronous tasks in JavaScript allow for non-blocking operations, improving performance and user experience.

• Use callbacks, promises, or async/await to handle asynchronous tasks

• Callbacks: Functions passed as arguments to be executed once the task is complete

• Promises: Objects representing the eventual completion or failure of an asynchronous operation

• Async/await: Syntactic sugar for promises, making asynchronous code look synchronous

• Example: Fetching data from an API, handlin...read more