How to use Jest for mocking in JavaScript tests

⚛️ Top Mistakes Developers Often Make in React.js (and How to Avoid Them) 🚫 No matter how long we’ve been coding, we’ve all made these mistakes at some point 👇 1️⃣ Not Using Keys Properly in Lists → Missing or using index as a key can cause re-rendering issues. ✅ Always use a unique id instead. 2️⃣ Mutating State Directly → Doing state.value = newValue won’t trigger a re-render. ✅ Always use the state setter (e.g., setValue(newValue)). 3️⃣ Overusing useEffect → Putting too much logic inside useEffect can lead to performance problems or infinite loops. ✅ Keep it focused — and always define dependencies properly. 4️⃣ Ignoring Component Reusability → Rewriting similar code multiple times. ✅ Break your UI into smaller, reusable components. 5️⃣ Not Handling Async Code Correctly → Forgetting to clean up async calls can cause memory leaks. ✅ Use cleanup functions or cancel tokens. 6️⃣ Forgetting Error Boundaries → A single runtime error can crash your entire UI. ✅ Wrap components in error boundaries for safety. Every mistake teaches something new — the key is to learn, refactor, and grow. 💪 What’s the biggest React mistake you made early on? 👇 #ReactJS #FrontendDevelopment #WebDevelopment #JavaScript #CodingTips

🚀 Promises (JavaScript) Promises provide a cleaner and more structured way to handle asynchronous operations in JavaScript. A promise represents the eventual completion (or failure) of an asynchronous operation and its resulting value. Promises help avoid callback hell and improve code readability and maintainability. Promises can be in one of three states: pending, fulfilled, or rejected. 🎓 Be curious. Be hungry. Be unstoppable! 💡 Knowledge at scale — 10,000+ concepts, 4,000+ articles, 12,000+ quiz questions. All AI-personalized! 📲 Download the app: https://lnkd.in/gefySfsc 🌐 Learn more: https://techielearn.in #JavaScript #WebDev #Frontend #JS #professional #career #development

🚀 Why Basics Matter More Than Frameworks Everyone wants to jump straight into React, Next.js, or whatever’s trending. But here’s the truth frameworks are shortcuts built on top of fundamentals. If you don’t understand the road, shortcuts only get you lost faster. I’ve worked with various developers who can build complex UIs but freeze when JavaScript behaves unexpectedly. That’s not a lack of skill, that’s a lack of foundation. When you master the core concepts 🔹 How the DOM actually works 🔹 How JS handles memory, scope, and events 🔹 How CSS paints and reflows 🔹 How HTTP and rendering really connect then any framework becomes just another tool, not a dependency. Frameworks change every few years. Basics stay forever. If you can write clean logic with vanilla JS, you’ll never fear the next big thing. Because the fundamentals never go out of fashion. Stay rooted. Build deep. That’s how you become better developer. #frontend #javascript #developers #careergrowth #learning

🚀 Lexical Scope and Closures (JavaScript) Lexical scope (also known as static scope) means that a function's scope is determined by its position in the source code. Closures are functions that have access to variables from their surrounding scope, even after the outer function has finished executing. This is because the inner function 'closes over' the variables in its lexical environment. Closures are a powerful feature of JavaScript, enabling data encapsulation and state preservation. Learn more on our app: https://lnkd.in/gefySfsc #JavaScript #WebDev #Frontend #JS #professional #career #development

I recently made a small optimization in my React project — and it improved the load time by almost 30%! It all came down to: ✅ Replacing heavy 3rd-party libraries with lighter ones ✅ Using React.lazy and Suspense for code splitting ✅ Loading only what’s needed (dynamic imports) Such a tiny tweak made a noticeable difference in performance — both in Lighthouse scores and real-user experience. Sometimes, the biggest wins come from the smallest changes 💡 Have you made a simple tweak that gave you big results? Let’s share optimization ideas 👇 #reactjs #webperformance #frontenddevelopment #javascript #nextjs #webdev

Ever wondered what a React component really is? It’s simpler than it sounds A React component is just a JavaScript function that returns markup. But here’s the twist: it doesn’t return HTML; it returns JSX! JSX looks like HTML but works like JavaScript; that’s what makes React so powerful and declarative. In simple words: Think of components as LEGO blocks reusable pieces that combine to build entire UIs. 🧩 One component for a button, one for a card, and one for a navbar and together, they make your app. #React #JavaScript #FrontendDevelopment #WebDevelopment #Learning #ReactJS #Frontend #Coding

🚀 The `setTimeout()` Function (JavaScript) The `setTimeout()` function allows you to execute a function after a specified delay in milliseconds. It is a fundamental tool for creating asynchronous behavior in JavaScript. The function passed to `setTimeout()` is added to the task queue and executed by the event loop when the delay has elapsed and the call stack is empty. `setTimeout` is often used to defer execution or schedule tasks for later. Learn more on our app: https://lnkd.in/gefySfsc #JavaScript #WebDev #Frontend #JS #professional #career #development

🚀 Mastering useReducer in React When working with React’s useReducer hook, developers often face tricky issues that can break state logic or cause unexpected re-renders. 👉 Here are some common mistakes you should watch out for 👇 1️⃣ Dispatching an action, but the screen doesn’t update. 2️⃣ A part of the reducer state becomes undefined after dispatching. 3️⃣ The entire reducer state becomes undefined after dispatching. 4️⃣ Error: “Too many re-renders.” 5️⃣ The reducer or initializer function runs twice Let’s write clean, predictable state logic 💪 #ReactJS #ReactHooks #useReducer #CommonMistake #WebDevelopment #Frontend #JavaScript

😂 The Developer’s Journey in One Line 😂 You learn JavaScript core concepts, master React fundamentals, discuss scalable design, explain optimization techniques, communicate like a pro 💬... and then 💀 you spend your day removing overflow: hidden or fighting that 3px gap because someone made it position: absolute without managing its z-index 😭 Ah yes — the true full-stack experience 😎 #WebDeveloper #ReactJS #FrontendHumor #CodingLife #DevStruggles #JavaScript #CSSWar #UIUX #TechLife #RelatableDev #FrontendDeveloper

When I first started learning React, I thought it was just another JavaScript framework. But after building my first real project… I realized React isn’t just a tool — it’s a way of thinking. 🧠 Here’s what it teaches you 👇 🔹 How to break big problems into small, reusable components 🔹 How to manage data flow, not just static layouts 🔹 How to think about state before style 🔹 How to keep your UI logic clean, predictable, and scalable Once that clicked — everything about frontend development started making sense. ✨ Now, I can’t imagine building without React. It’s fast, modular, and honestly… addictive in the best way possible 🚀 💬 What’s one React concept that completely changed your way of coding? #ReactJS #FrontendDevelopment #JavaScript #WebDevelopment #DeveloperJourney #CleanCode #CodeLife