EPAM Systems Front end Developer Interview Questions and Answers

Event bubbling is the process of propagating an event from the innermost element to its parent elements in the DOM hierarchy.

• Events in JavaScript are triggered on elements and then propagate up the DOM tree.

• During event bubbling, an event triggered on a child element will also trigger on its parent elements.

• This allows for event delegation, where a single event handler can be used for multiple elements.

• Event.stopPropag...read more

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

Use the accept attribute in the input tag to only allow jpg and png files.

• Add accept attribute to input tag with 'image/jpeg, image/png' value

• This will restrict file selection to only jpg and png files

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.

Use React Router's Redirect component to redirect to login page if user is not logged in.

• Create a PrivateRoute component that checks if user is logged in

• If user is not logged in, redirect to login page using Redirect component

• Wrap the routes that require authentication with PrivateRoute component

SQL Server stored procedures and functions

• Stored procedures are precompiled SQL statements that can be executed with parameters

• Functions return a single value and can be used in SQL statements

• Both can improve performance and security by reducing network traffic and preventing SQL injection attacks

ASP.NET page life cycle is a series of events that occur when a page is requested, processed, and rendered.

• Page request is received by the server

• Page is initialized and controls are created

• Page is loaded with data and events are triggered

• Page is rendered and sent to the client

• Page is unloaded and disposed