10+ Perficient Interview Questions and Answers

Event Loop is a mechanism in JavaScript that manages the execution of code and handles asynchronous operations.

• Event Loop continuously checks the call stack and the message queue.

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

• If the message is a callback function, it is executed and removed from the call stack.

• If the message is not a callback function, it is passed to the relevant API for execution.

• Once the API has fini...read more

State in functional components can be managed using the useState hook in React.

• Use the useState hook to declare state variables in functional components.

• useState returns an array with the current state value and a function to update that value.

• Example: const [count, setCount] = useState(0);

• State variables should be immutable, so always use the setter function to update them.

JavaScript Promise is an object representing the eventual completion or failure of an asynchronous operation.

• Promises are used to handle asynchronous operations such as fetching data from an API.

• They have three states: pending, fulfilled, or rejected.

• Promises can be chained using .then() and .catch() methods.

• Promises can also be created using the Promise constructor.

Event loop in JavaScript is responsible for handling asynchronous operations by executing callback functions in a non-blocking way.

• Event loop is a mechanism that allows JavaScript to perform non-blocking operations.

• It continuously checks the call stack and the callback queue to see if there are any functions that need to be executed.

• If the call stack is empty, it takes the first function from the callback queue and pushes it onto the call stack for execution.

• This process allo...read more

Use CSS to make a set of 6 boxes responsive

• Use percentage or viewport units for width and height

• Use media queries to adjust styles for different screen sizes

• Consider using flexbox or grid for layout

• Avoid using fixed pixel values

• Test on different devices and browsers

• Use CSS frameworks like Bootstrap or Foundation for easier implementation

Generate an array of prime numbers from 1 to 100.

• Iterate from 1 to 100 and check if each number is prime

• A prime number is only divisible by 1 and itself

• Start with a list of prime numbers and check divisibility

Hosting in JavaScript refers to the process of declaring a variable or function before it is used in the code.

• Hosting allows you to use variables and functions before they are declared in the code.

• Variables are hoisted to the top of their scope, while functions are fully hoisted.

• Example: console.log(myVar); var myVar = 10; This will not throw an error because 'myVar' is hoisted to the top of the scope.

DOM stands for Document Object Model, which is a programming interface for web documents.

• DOM is a representation of the structure of a web page, allowing scripts to dynamically access and update the content, structure, and style of the document.

• It provides a way for scripts to interact with the web page by accessing and manipulating elements like text, images, forms, etc.

• DOM is platform and language-independent, allowing developers to use it with any programming language that...read more

Promises in TypeScript are objects representing the eventual completion or failure of an asynchronous operation.

• Promises are used to handle asynchronous operations in a more readable and manageable way.

• They can be in one of three states: pending, fulfilled, or rejected.

• Promises can be chained using .then() to handle success and .catch() to handle errors.

• Example: const myPromise = new Promise((resolve, reject) => { ... });

Hooks in JavaScript are functions that let you use state and other React features without writing a class.

• Hooks were introduced in React 16.8 to allow functional components to have state and lifecycle methods.

• useState() is a hook that allows you to add state to functional components.

• useEffect() is a hook that allows you to perform side effects in functional components.

• Custom hooks are functions that allow you to reuse stateful logic across multiple components.