Question 1

What is the main difference between let and var in JavaScript?

Accepted Answer

let has block scope while var has function scope. This means a variable declared with let is only accessible within the block where it's defined (between curly braces), whereas var is accessible throughout the entire function. This difference is crucial to avoid bugs related to hoisting and variables leaking outside their intended context.

Question 2

What happens when accessing a let variable before its declaration?

Accepted Answer

A ReferenceError is thrown because the variable is in the Temporal Dead Zone (TDZ). Unlike var which is hoisted with undefined value, let variables are hoisted but remain inaccessible until their declaration. This temporal dead zone helps detect programming errors where a variable is used before being defined.

Question 3

What is the main characteristic of const in JavaScript?

Accepted Answer

const prevents reference reassignment but not content mutation. For primitive types, this means the value cannot change. For objects and arrays, the reference stays the same but properties or elements can be modified. Using const by default is good practice as it expresses the intent not to reassign the variable.

JavaScript Essentials

What is the main difference between let and var in JavaScript?

Відповідь

What happens when accessing a let variable before its declaration?

Відповідь

What is the main characteristic of const in JavaScript?

Відповідь

What are the primitive types in JavaScript?

What is the result of typeof null in JavaScript?

Інші теми співбесід React Native

React Fundamentals

React Native Basics

React Hooks

TypeScript for React & React Native

React Native Components & API

React Native Styling & Layout

React Native Navigation

React Native State Management

React Native Networking & API

Data Persistence

Forms & Validation

React Native Animations

Native Modules & Bridge

Platform-Specific Code

Permissions & Device APIs

Push Notifications

React Native Testing

React Native Debugging

Build & Deployment

Expo vs React Native Bare

Performance Optimization

Memory Management

Architecture Patterns

React Native New Architecture

Security Best Practices

Offline-First Architecture

React Native CI/CD

Monorepo & Code Sharing

Advanced Topics

App Lifecycle & Background Execution

Authentication & Session Management

Monitoring & Crash Reporting

Опануй React Native для наступної співбесіди