User Interface and Frontend Developer Interview Questions and Answers

display none removes element from layout, visibility hidden hides element but still takes up space

• display none removes element from layout flow

• visibility hidden hides element but still takes up space

• display none is more efficient for hiding elements

• visibility hidden is better for hiding elements while keeping layout intact

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 denoted by three dots (...) and is used to spread array elements or object properties.

• Rest operator is also denoted by three dots (...) and is used to collect multiple elements into a single array.

• Spread operator can be used to concatenate arrays or objects, while rest operator can be used to gather function arguments...read more

ES6 features are new additions to JavaScript introduced in ECMAScript 2015.

• Arrow functions for more concise syntax: const add = (a, b) => a + b;

• Let and const for block-scoped variables: let x = 5; const y = 10;

• Template literals for easier string interpolation: const name = 'John'; console.log(`Hello, ${name}!`);

• Classes for object-oriented programming: class Person { constructor(name) { this.name = name; } }

• Destructuring assignment for easily extracting values from objects or ...read more

A high order function is a function that takes one or more functions as arguments or returns a function as its result.

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

• They can be used to abstract and encapsulate common patterns in code.

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

var is function scoped, let is block scoped, const is block scoped and cannot be reassigned.

• var is function scoped

• let is block scoped

• const is block scoped and cannot be reassigned

Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope.

• Variable declarations are hoisted to the top of their scope but not their initializations.

• Function declarations are fully hoisted, including their definitions.

• Hoisting can lead to unexpected behavior if not understood properly.

Hooks in ReactJS 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 can be created to reuse logic across multiple components.