1000+ Front end Developer Interview Questions and Answers

Use flexbox to center align a div in just one line in CSS.

• Set the parent container's display property to flex.

• Use the justify-content property with the value 'center' to horizontally center the div.

• Use the align-items property with the value 'center' to vertically center the div.

Check if a given string is a palindrome considering only alphanumeric characters.

• Remove non-alphanumeric characters from the input string.

• Compare the string with its reverse to check for palindrome.

• Handle edge cases like empty string or single character input.

• Use two pointers approach for efficient comparison.

Implement Priority CPU Scheduling algorithm to compute waiting time and turn-around time for processes.

• Implement a function that takes in burst times, priorities, and number of processes as input

• Sort the processes based on priority, with lower process ID as tiebreaker

• Calculate waiting time and turn-around time for each process based on the scheduling algorithm

Javascript is single-threaded.

• Javascript runs on a single thread called the event loop.

• This means that it can only execute one task at a time.

• However, it can delegate tasks to other threads using web workers.

• This allows for parallel processing without blocking the main thread.

Implement a calculator class with chaining methods and delay function.

• Create a Calculator class with add, sub, mul methods that return the instance of the class.

• Implement a delay method that uses setTimeout and returns the instance of the class.

• Use a queue to store the operations and execute them in order after the delay.

• Return the result of the operations when the equals method is called.

JavaScript code to synchronize checkbox states in a nested structure.

• Use event delegation to handle checkbox clicks efficiently.

• Recursively traverse the DOM to find child checkboxes.

• Set the checked property of child checkboxes based on the parent checkbox state.

• Example: If a parent checkbox is checked, all its children should also be checked.

Create a function that manages an array with methods to get, add, and delete elements.

• Define a function that returns an object with methods.

• Use an array to store elements internally.

• Implement a 'getElements' method to return the array.

• Implement an 'addElement' method to push a new element to the array.

• Implement a 'deleteElement' method to remove an element by value.

React Native works by using a bridge to communicate between JavaScript and native code on iOS and Android devices.

• React Native uses a JavaScript thread to handle logic and a separate thread for UI rendering.

• The bridge allows for communication between the JavaScript thread and native code on the device.

• React Native uses a virtual DOM to optimize rendering performance.

• Memory allocation is handled by the device's operating system.

• React Native also provides tools for debugging an...read more

JavaScript data types include string, number, boolean, object, function, undefined, and null.

• String: 'hello'

• Number: 42

• Boolean: true or false

• Object: { key: 'value' }

• Function: function() { }

• Undefined: undefined

• Null: null

Remove duplicate elements from an Array

• Use the Set object to remove duplicate elements

• Convert the Set back to an array using the spread operator

• If the array contains objects, use a custom comparison function

Inheritance is a relationship between a superclass and subclass, while generalization is a relationship between entities with common characteristics.

• Inheritance involves a parent-child relationship where the child class inherits attributes and methods from the parent class.

• Generalization involves grouping entities with common attributes into a higher-level entity.

• Inheritance is a specific form of generalization in object-oriented programming.

• Example: In a database, a 'Car' en...read more

CSS media queries are used to apply different styles based on device characteristics. Min and max define the range of values.

• Media queries allow for responsive design by adapting to different screen sizes and orientations

• Min-width and max-width are commonly used to define the range of screen sizes

• Min-device-width and max-device-width are used to target specific device characteristics

• Other media query features include min-height, max-height, orientation, and resolution

var is function scoped while let is block scoped in JavaScript.

• var is function scoped, meaning it is accessible throughout the function it is declared in.

• let is block scoped, meaning it is only accessible within the block it is declared in.

• Using var can lead to variable hoisting issues, while let avoids this problem.

• Example: var x = 10; function test() { var x = 20; console.log(x); } test(); // Output: 20

JavaScript is considered a dynamic language because variables can change types based on their current value.

• Variables in JavaScript can hold different types of values at different times

• The type of a variable is determined at runtime, not at compile time

• Dynamic typing allows for flexibility and ease of use in JavaScript programming

• Example: a variable can start as a number and then be reassigned as a string

Functional components and class components are not the same in React. Functional components are simpler and more lightweight, while class components have additional features like state and lifecycle methods.

• Functional components are stateless and are just JavaScript functions that return JSX.

• Class components have access to state and lifecycle methods like componentDidMount and componentDidUpdate.

• Functional components are easier to read and test, while class components can be ...read more

Debounce the API call on input change to optimize performance.

• Implement a debounce function to delay the API call until the user has finished typing.

• Set a time interval for the debounce function to wait before making the API call.

• Cancel the previous API call if a new input change occurs before the time interval is up.

• Use a loading spinner to indicate to the user that the API call is in progress.

• Consider using a caching mechanism to store the API response for future use.

Futuristic skills for a frontend developer include AI, VR/AR, PWAs, and accessibility.

• Proficiency in AI and machine learning for creating intelligent interfaces

• Knowledge of VR/AR for developing immersive experiences

• Expertise in Progressive Web Apps (PWAs) for building fast and reliable web applications

• Understanding of accessibility guidelines and techniques for creating inclusive designs

jQuery is a fast, small, and feature-rich JavaScript library.

• jQuery simplifies HTML document traversing, event handling, and animating.

• It provides a set of methods for AJAX interactions and DOM manipulation.

• jQuery is cross-platform and supports a wide range of browsers.

• It has a large community and a vast number of plugins available.

• Project architecture depends on the specific project and its requirements.

The process of building a front-end project involves planning, designing, coding, testing, and deploying.

• Gather requirements and create a project plan

• Design the user interface using tools like Figma or Sketch

• Code the front-end using HTML, CSS, and JavaScript

• Test the project for bugs and usability

• Deploy the project to a web server or hosting platform

Develop an app to show all airports in a country on a map and allow users to report incidents after logging in.

• Use a map API like Google Maps or Mapbox to display all airports in the country

• Implement a login system for users to report incidents

• Create a form for users to report incidents with fields like airport name, incident type, and description

• Store incident reports in a database for future reference and analysis

The filter method is a built-in JavaScript method used to create a new array with all elements that pass a certain condition.

• Filter method is more concise and readable compared to for loop

• Filter method is more declarative and functional programming oriented

• Example: const numbers = [1, 2, 3, 4, 5]; const evenNumbers = numbers.filter(num => num % 2 === 0);

• Example: const words = ['hello', 'world', 'example']; const shortWords = words.filter(word => word.length < 6);

Data can be shared between components in Angular using services, input/output properties, and observables.

• Use services to create a shared data service that can be injected into multiple components

• Use input/output properties to pass data from parent to child components

• Use observables to create a data stream that can be subscribed to by multiple components

typeof() operator in JavaScript is used to determine the data type of a variable or expression.

• typeof() returns a string indicating the type of the operand.

• Example: typeof 42 will return 'number'.

• Example: typeof 'hello' will return 'string'.

Components in React go through various stages like mounting, updating, and unmounting.

• Components are created and inserted into the DOM during the mounting phase.

• During the updating phase, components can re-render due to changes in props or state.

• Components are removed from the DOM during the unmounting phase.

• Lifecycle methods like componentDidMount, componentDidUpdate, and componentWillUnmount are used to perform actions at different stages.

Prototype chaining in JavaScript is the mechanism by which objects inherit properties and methods from other objects.

• In JavaScript, each object has a prototype property that points to another object. When a property or method is accessed on an object, JavaScript will look for it in the object itself first, and then in its prototype chain.

• If the property or method is not found in the object, JavaScript will continue to look up the prototype chain until it finds the property or...read more

HTML5 is the latest version of the HTML standard with new features for web development.

• Support for multimedia elements like <video> and <audio>

• Canvas and SVG for graphics and animations

• Improved form controls and validation

• Offline storage with Local Storage and IndexedDB

• Geolocation API for location-based services

The 'this' operator in JavaScript refers to the current context or object.

• Refers to the current object or context in which a function is being executed

• Can be used to access properties and methods of the current object

• The value of 'this' is determined by how a function is called