React Interview Mastery is the most complete, end-to-end
 interview preparation program ever created for React developers. Whether
 you're preparing for your first junior role, aiming to become
 a strong mid-level engineer, or targeting a
 senior front-end position, this course gives you everything
 you need to confidently pass technical and behavioral interviews at top
 companies.



 Across 16 structured modules, you’ll move from mastering the
 fundamentals of rendering, components, hooks, and state… to advanced concepts
 like performance optimization, Redux Toolkit, global state architecture,
 routing internals, complex forms, React Query, TypeScript patterns, and even
 React’s fiber, scheduling, and concurrent rendering system.


But this course goes far beyond technical knowledge.


 You’ll also learn how to communicate your decisions clearly, demonstrate
 ownership and leadership, avoid common behavioral traps, and practice with
 full simulation-style interviews—both technical and behavioral—designed
 exactly like real-world companies use.



 By the end of this program, you won’t just answer interview questions —
 you’ll understand React deeply, think like a senior engineer, and
 communicate like a confident professional.



 This course is your complete roadmap to becoming a standout React developer.


<hr />

<h2>What You Will Learn</h2>

<h3>✅ React fundamentals required for every junior interview</h3>
<ul>
 <li>Rendering and reconciliation</li>
 <li>JSX, components, and props</li>
 <li>State vs props and one-way data flow</li>
 <li>Event handling and synthetic events</li>
 <li>Lists, keys, and component structure</li>
</ul>

<h3>✅ Advanced React and JavaScript concepts used in real interview rounds</h3>
<ul>
 <li>Closures in the context of hooks</li>
 <li>Asynchronous behavior and React state updates</li>
 <li>Immutability and referential equality</li>
 <li>JavaScript execution model and its impact on React</li>
</ul>

<h3>✅ Hooks, performance, architecture, and deep React knowledge</h3>
<ul>
 <li>
 <code>useState</code>, <code>useEffect</code>, <code>useCallback</code>,
 <code>useMemo</code>, <code>useReducer</code>, and custom hooks
 </li>
 <li>React.memo, render behavior, and common performance pitfalls</li>
 <li>Diagnosing and fixing unnecessary re-renders</li>
</ul>

<h3>✅ Global state mastery</h3>
<ul>
 <li>Context API fundamentals and limitations</li>
 <li>Redux and Redux Toolkit applied to real-world scenarios</li>
 <li>Selectors, middleware, thunks, and async state logic</li>
 <li>Choosing between Context, Redux, and other tools</li>
</ul>

<h3>✅ Professional React architecture</h3>
<ul>
 <li>Component patterns and scalable structures</li>
 <li>Container vs presentational components</li>
 <li>Routing, code splitting, and navigation strategies</li>
 <li>SSR, CSR, ISR, and performance-driven architectural choices</li>
</ul>

<h3>✅ TypeScript for React interviews</h3>
<ul>
 <li>Typing props, state, and events</li>
 <li>Generics in React components and hooks</li>
 <li>Typing custom hooks and complex UI logic</li>
 <li>Advanced TypeScript patterns commonly asked in interviews</li>
</ul>

<h3>✅ Async patterns and real-world data fetching</h3>
<ul>
 <li>Using Fetch, Axios, and AbortController correctly</li>
 <li>React Query for declarative data fetching and caching</li>
 <li>Caching, refetching, and stale-while-revalidate patterns</li>
 <li>Handling race conditions, parallel fetching, and retries</li>
</ul>

<h3>✅ Behavioral interview excellence</h3>
<ul>
 <li>Telling your story using STAR with React-focused examples</li>
 <li>Communicating technical decisions clearly and confidently</li>
 <li>Handling conflict, feedback, and code reviews professionally</li>
 <li>Demonstrating ownership, leadership, and real impact</li>
 <li>Avoiding common behavioral interview traps</li>
</ul>

<h3>✅ Full mock interview simulations</h3>
<ul>
 <li>End-to-end behavioral interview simulations</li>
 <li>Scenario-based technical discussions about React systems</li>
 <li>Answering like a senior engineer, not just a coder</li>
</ul>

<hr />

<h2>Who This Course Is For</h2>
<ul>
 <li>Junior developers preparing for their first React job</li>
 <li>Mid-level developers targeting higher-paying roles</li>
 <li>Senior engineers polishing system design and communication</li>
 <li>Developers transitioning into frontend engineering</li>
 <li>
 Anyone who wants to understand React at a deeper, interview-ready level
 </li>
</ul>

<hr />

<h2>Outcome</h2>
By the end of this course, you will be able to:
<ul>
 <li>Confidently answer React interview questions at all levels</li>
 <li>Demonstrate real engineering thinking and problem-solving</li>
 <li>Communicate decisions like an experienced professional</li>
 <li>Architect React solutions and explain them clearly</li>
 <li>Excel in both technical and behavioral interviews</li>
 <li>
 Present yourself as a strong React engineer ready for modern product teams
 </li>
</ul>

Master every React interview topic from fundamentals to senior-level internals, hooks, performance optimization, state management, system design, TypeScript, data fetching, and behavioral interviews. This comprehensive course prepares you for real React job interviews with actionable sessions, hands-on scenarios, and full mock interviews.

React Interview Mastery | The Complete Roadmap for Junior to Senior Frontend Engineers

This module builds the core understanding a junior React candidate must demonstrate in interviews, covering rendering basics, JSX, components, props, state management, events, and list rendering.

React Fundamentals for Junior Interviews

Understanding How React Works (Rendering & Reconciliation Basics)

JSX, Components, and Props Fundamentals

State vs. Props and One-Way Data Flow

Event Handling and Synthetic Events

Conditional Rendering and Lists/Keys

This module prepares candidates to handle advanced JavaScript questions specifically in the context of React interviews, including closures with hooks, async behavior, immutability, referential equality, binding, and how JavaScript's execution model impacts rendering.

Advanced JavaScript Concepts for React

Closures and Their Impact on Hooks

Asynchronous Behavior and React State Updates

Immutability, Referential Equality, and Rendering

Deep Dive on This, Bind, and Arrow Functions in React

JavaScript Execution Model and Its Effect on React

This module prepares candidates to master the React hooks that appear in nearly every junior and mid-level interview, covering useState, useEffect, useRef, useReducer, and custom hooks with deeply React-focused explanations.

React Hooks (Junior → Mid-Level Core Questions)

useState: State Updates, Batching, and Pitfalls

useEffect: Dependencies, Cleanup, and Stale Closures

useRef: Mutable Values, DOM Access, and Performance

useReducer: When and Why to Replace useState

Custom Hooks: Reusability and Real Interview Patterns

This module prepares candidates to confidently handle React performance interview questions by mastering rendering behavior, memoization hooks, React.memo, and real-world re-render debugging patterns.

Performance Optimization in React

React Rendering Cycle and Common Performance Traps

useMemo: Preventing Expensive Recomputations

useCallback: Stabilizing Callback References

React.memo: Shallow Comparison and Pitfalls

Fixing Re-Renders in Real Interview Scenarios

This module prepares candidates to confidently handle React interview questions related to the Context API, global state management, performance issues, and how Context compares to Redux in real-world architecture and interview scenarios.

Context API and Global State

Context API Fundamentals and Avoiding Overuse

Performance Problems with Context (Propagation & Re-Renders)

When Context is Better/Worse Than Redux

Building Scalable Context Architectures

Interview Scenarios Comparing Context vs Redux

This module prepares candidates to confidently answer Redux and Redux Toolkit interview questions by mastering reducers, actions, selectors, dispatching patterns, middleware, and real-world async/architecture scenarios.

Redux & Modern State Management

Redux Core Concepts (Actions, Reducers, Store)

Modern Redux Toolkit Deep Dive

useSelector, useDispatch, and Performance Issues

Middleware, Thunks, and Async Logic

Advanced Interview Scenarios with Redux Toolkit

This module prepares candidates to confidently answer React interview questions about component composition, design patterns, architectural decisions, and scalability techniques used in real-world applications.

Component Design, Patterns & Architecture

Container vs Presentational Components

Controlled vs Uncontrolled Components

Compound Component Pattern

Render Props & Higher Order Components

Clean Architecture for Scalable React Apps

This module prepares candidates to answer React Router interview questions confidently by deeply understanding client-side routing, navigation, parameters, protected routes, and routing performance patterns.

React Router & Navigation

Core Concepts of Client-Side Routing

Dynamic Routes and Route Parameters

Protected Routes and Authentication Patterns

Lazy Loading & Code Splitting with Routing

Advanced Interview Questions on Routing Internals

This module prepares candidates to confidently answer interview questions about managing user input, controlled and uncontrolled components, form libraries, validation strategies, debouncing, throttling, and complex real-world form scenarios.

Forms, Validation & User Input

Controlled Components in Depth

Uncontrolled Components and Refs

Formik, React Hook Form, and Performance

Debouncing, Throttling, and Input Optimization

Real Interview Scenarios with Complex Forms

This module prepares candidates to confidently answer interview questions about unit testing, component testing, mocks, E2E testing, and writing testable React components.

Testing in React

Unit Testing with Jest

Component Testing with React Testing Library

Mocking Fetch, APIs, and State

End-to-End Testing Concepts (Playwright/Cypress)

Writing Testable React Components (Interview Patterns)

This module prepares senior-level candidates to explain React’s inner workings, including Fiber, reconciliation, scheduling, concurrent rendering, and the render–commit lifecycle.

React Internals (Senior-Level Only)

How React Reconciliation and Fiber Work

Concurrent Rendering in React 18

Scheduling, Priorities, and Interruptible Rendering

How useEffect and useLayoutEffect Actually Work Internally

What Happens During a Render → Commit Cycle

This module prepares candidates to design scalable, maintainable, and high-performance React systems using real-world architecture patterns expected in senior frontend interviews.

Real System Design for Frontend Engineers

Design a Scalable React Application

How to Structure Large Component Trees

State Management Strategy Decision-Making

Performance Budgeting and SSR/CSR/ISR Choices

Designing a Production-Ready Frontend Architecture

This module prepares candidates to confidently answer React + TypeScript interview questions, covering typed props, events, generics, custom hooks, discriminated unions, and advanced patterns expected in senior interviews.

React + TypeScript

Typing Props, State, and Events

Generics in React Components and Hooks

Typing Custom Hooks

Discriminated Unions for UI Logic

Advanced TS Patterns for Senior Interviews

This module prepares candidates for React interview questions around data fetching, async patterns, React Query, caching, race conditions, and reliable loading strategies.

Data Fetching & Async Patterns

Fetch, Axios, and AbortController

React Query Interview Deep Dive

Caching, Refetching, and Stale-While-Revalidate

Handling Race Conditions & Parallel Fetching

Patterns for Reliable Data Loading in React

This module prepares candidates for behavioral interviews by helping them communicate clearly, demonstrate technical ownership, showcase leadership, and avoid common behavioral pitfalls.

Behavioral Interview Mastery for Frontend Developers

How to Tell Your Story (STAR + React Projects)

How to Communicate Technical Decisions Clearly

How to Handle Conflict and Code Review Scenarios

How to Demonstrate Ownership, Leadership, and Impact

Avoiding Behavioral Interview Traps

This module delivers complete behavioral interview simulations tailored for frontend and React engineers, helping candidates answer realistically, confidently, and impactfully.

Full Behavioral Interview Simulation

Tell me about a difficult bug you fixed Simulation

Tell me about a time you disagreed with your team Simulation

Describe a system you built end-to-end Simulation

What’s a mistake you made and how did you fix it Simulation

Final Mock Interview (All Behavioral Patterns)

React Interview Mastery: From Fundamentals to Senior-Level System Design

Explore the main AI career roles including Data Scientist, Machine Learning Engineer, Deep Learning Engineer, AI Engineer, and MLOps. Learn what each role does, required skills, and a step-by-step roadmap with real project ideas to choose the right AI career path.

Tech Tips By Moh | AI Career Paths and Roadmaps for Modern AI Roles

AI Career Paths and Roadmaps for Modern AI Roles

A comprehensive guide to Artificial Intelligence — including its history, core concepts like machine learning and neural networks, real-world applications, ethical concerns, and future trends shaping technology and society.

Exploring the World of Artificial Intelligence

Learn how to use OpenAI API for developing AI-driven solutions, including creating projects like ChatGPT, with a focus on reusable and scalable coding practices using Django for backend development.

Tech Tips By Moh | Creating AI-driven Solutions with OpenAI API

Creating AI-driven Solutions with OpenAI API

<h2>Live Progress Updates in Long-Running Backend Tasks: Polling vs WebSocket</h2> When your backend is handling long tasks like crunching big files, training a model, or working with AI APIs showing just a spinner until it&rsquo;s done is painful for users. A better way? Show live progress updates while the task is running, so users know something is happening. &nbsp; <h3>Why Live Updates Matter:</h3> Nobody likes waiting in the dark. Imagine uploading a 500-page PDF and staring at a loader for minutes. Instead, if the app shows progress updates after each page, users stay engaged and can even start using partial results before everything finishes. It makes the whole experience feel faster and more interactive. <h3>Method 1: Polling</h3> How it works The frontend keeps asking the backend every few seconds: &ldquo;What&rsquo;s the progress now?&rdquo; 1. User starts a task. 2. Backend processes the work. 3. Progress is stored (e.g., in Redis) with a unique ID. 4. Frontend hits a &ldquo;progress&rdquo; endpoint on repeat. 5. Backend returns the current status until the task is done. &nbsp; Pros: Super easy to implement. Works everywhere, no special setup. Cons: More network traffic (lots of repeated requests). Updates are tied to the polling interval, not truly real-time. &nbsp; <h3>Method 2: WebSocket</h3> How it works Instead of asking again and again, the frontend opens a WebSocket connection. From there, the backend can push updates instantly as they happen. Typical flow: 1. Frontend opens a WebSocket connection. 2. Backend runs the task and streams progress updates over that connection. 3. Frontend updates the UI immediately. Pros: Real-time updates with no delay. Less network overhead. Perfect for live dashboards, chat apps, and AI progress updates. Cons: More complex to set up and scale. Requires support on both frontend and backend. &nbsp; <h3>Practical Example:</h3> Here&rsquo;s a simple Python example to simulate progress: import time for i in range(101):&nbsp; # 0 to 100% &nbsp;&nbsp;&nbsp; time.sleep(0.2)&nbsp;&nbsp; # simulate work &nbsp;&nbsp;&nbsp; # send progress via cache (Polling) or WebSocket <ul> <li>With Polling, you&rsquo;d write progress to cache and let the frontend check it on intervals.</li> <li>With WebSocket, you&rsquo;d push progress directly to the client every step.</li> </ul> <h3>When to Use Polling vs WebSocket</h3> Polling is a good fit when: <ul> <li>Setting up WebSockets is hard in your environment. </li> <li>You don&rsquo;t need instant updates.</li> </ul> WebSocket is better when: <ul> <li>You want real-time, no-delay updates. </li> <li>You&rsquo;d like to cut down on repeated HTTP calls.</li> <li>Your app is interactive (chat, live feeds, dashboards).</li> </ul> <h3>Conclusion:</h3> Live progress updates change the way users experience your app. Whether it&rsquo;s AI, data crunching, or file handling showing progress in real time keeps users confident and engaged. Polling is simple and reliable; WebSocket is faster and more interactive. Pick the one that fits your setup best. Pro Tip: Using Django? Try Django Channels for WebSockets and Redis for progress tracking in both approaches.

Learn how to improve user experience in long-running backend tasks with live progress updates. Compare Polling vs WebSocket and choose the best real-time solution.

Live Progress Updates in Long-Running Backend Tasks: Polling vs WebSocket | Tech Tips By Moh

Live Progress Updates in Long-Running Backend Tasks: Polling vs WebSocket

<h2>Remove Image Background and Blend Images Using Python</h2>


 Looking to elevate your Python image processing skills? In this guide, you'll learn how to remove the background from an image using Python and blend it with another image using NumPy. It’s a simple yet powerful technique I recently shared in a video tutorial.


<h3>🎬 What This Tutorial Covers</h3>


 We'll walk through the process of combining two powerful Python libraries — rembg and NumPy — to create clean, professional-looking image composites. This is perfect for:


<ul>
 <li>Automating image post-processing workflows</li>
 <li>Creating thumbnails and social media visuals</li>
 <li>Building tools for AI/ML datasets</li>
 <li>Designing profile images or marketing content</li>
</ul>

<h3>📌 Step 1: Remove the Image Background with rembg</h3>


 The <a href="https://github.com/danielgatis/rembg" target="_blank" rel="noopener noreferrer">rembg Python library</a> lets you remove an image’s background using deep learning — no manual editing needed.


To remove a background:

<ol>
 <li>Install the rembg library using pip.</li>
 <li>Read the image file in binary mode.</li>
 <li>Pass the binary data to the remove function from rembg.</li>
 <li>Convert the output into an image and save it in PNG format.</li>
</ol>


 This results in a clean, background-free image that you can easily layer or reuse.


<h3>📌 Step 2: Blend Foreground and Background with NumPy</h3>


 Once you have the image without a background, you can blend it with a new background image using NumPy. Here’s how the process works:


<ol>
 <li>Resize both the foreground and background images to match in dimensions.</li>
 <li>Convert both images into NumPy arrays and use float values for blending.</li>
 <li>Apply a weighted sum using your preferred blend ratios (e.g., 80% foreground and 20% background).</li>
 <li>Convert the final array back into an image and save it as your final result.</li>
</ol>


 This lets you control how much of each image appears in the final result. You can experiment with different weights for creative effects.


<h3>📦 Full Code and GitHub Repository</h3>


 Want to try it yourself? I’ve published a complete working example you can clone and run. It includes sample images and instructions:



 👉 <a href="https://github.com/mmmohajer/image-overlay-and-grayscale" target="_blank" rel="noopener noreferrer">Image Background Removal and Blending – GitHub Repository</a>


<h3>🌟 Final Thoughts</h3>


 By combining rembg, Pillow, and NumPy, you can create powerful workflows for creative image editing, AI preprocessing, or content generation. Whether you're automating image cleanups or making dynamic visuals, this technique is a great place to start.



 If this tutorial was helpful, feel free to explore more on my GitHub or share this guide with fellow Python enthusiasts!

Learn how to remove image backgrounds using Python’s rembg library and blend images with NumPy for stunning effects. Explore the full code and try it yourself!

Removing Backgrounds and Blending Images with Python: A Simple Guide| Tech Tips By Moh

Removing Backgrounds and Blending Images with Python: A Simple Guide

If you&rsquo;re starting your journey in web development, you&rsquo;ve probably heard advice like this: &ldquo;Learn JavaScript, Python, and C++&mdash;you&rsquo;ll be a full-stack developer in no time!&rdquo; &ldquo;Master frontend and backend together&mdash;it&rsquo;s the fastest way to get a job!&rdquo; It sounds promising, but here&rsquo;s the truth: Trying to learn too many programming languages and frameworks at once is the fastest way to get stuck. <h2>Why Learning Too Many Languages Can Hurt Your Progress</h2> When new developers try to juggle multiple languages like JavaScript, Python, C++, and Java all at the same time, they spread their energy too thin. It&rsquo;s overwhelming, and instead of becoming a master in one area, they end up with surface-level knowledge that doesn&rsquo;t help them land a job or build real projects. This problem is so common that I made a video about it&mdash;watch it now to avoid falling into this trap! <h2>Why You Should Focus on One Language or Framework</h2> Here&rsquo;s the truth: ✅ Depth beats breadth. Learning one language deeply&mdash;like JavaScript with React for frontend or Python with Django for backend&mdash;helps you build real-world projects and solve real problems. ✅ Confidence comes from mastery. When you understand the core concepts of one stack, you&rsquo;ll find it much easier to pick up new tools later, like Docker, Redis, or CI/CD pipelines. ✅ Projects matter more than tutorials. Building a few solid projects teaches you far more than watching endless courses. <h2>How My Mentoring Can Help You</h2> If you feel overwhelmed by all the options, don&rsquo;t worry&mdash;you&rsquo;re not alone. In my mentoring program for aspiring web developers, I&rsquo;ll help you: <ul> <li> Choose the right tech stack based on your goals (e.g., frontend with React or backend with Django). </li> <li> Build hands-on projects that strengthen your skills. </li> <li> Stay focused on what really matters, so you can avoid getting distracted by the latest shiny tools. </li> </ul> The best part? The<a href="https://calendly.com/mohammad-aqd6/30min"> first mentoring session is free</a>&mdash;we&rsquo;ll explore your goals, your current skills, and create a clear, personalized plan for your learning journey. <hr> <h2>👩&zwj;💻 Ready to Start Your Web Development Journey the Right Way?</h2> 🎯 <a href="https://calendly.com/mohammad-aqd6/30min">Book your free mentoring session today</a> and let&rsquo;s build a roadmap for your success.

New web developers often struggle by learning too many programming languages at once. This blog explains why focusing on one language like JavaScript or Python can boost your skills and career faster.

The Biggest Mistake New Developers Make | Tech Tips By Moh

The Biggest Mistake New Developers Make