Can you cancel a Promise in JavaScript? Short answer: No — but you can cancel the work behind it. A Promise is just a result container, not the async operation itself. Once created, it will resolve or reject — you can’t “stop” it directly. What you can do instead: • Use AbortController → cancels APIs like fetch • Use cancellation flags/tokens → for custom async logic • Clear timers → if work is scheduled (setTimeout) • Ignore results → soft cancel pattern Real-world takeaway: Design your async code to be cancel-aware, not Promise-dependent. This is exactly how modern tools like React Query handle requests under the hood. #JavaScript #Frontend #AsyncProgramming #WebDevelopment #ReactJS #CleanCode
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Most developers don’t misunderstand JavaScript. They misunderstand time. . Take setTimeout vs setImmediate. On the surface, they look interchangeable. “Just run this later,” right? That’s the lie. Here’s the reality: setTimeout(fn, 0) → runs after the current call stack + timers phase setImmediate(fn) → runs in the check phase, right after I/O So under load or inside I/O cycles… they don’t behave the same at all. Example: You’re handling a heavy I/O operation (like reading a file or API response). setTimeout → might delay execution unpredictably setImmediate → executes right after the I/O completes One is scheduled. The other is strategically placed in the event loop. That difference? It’s the kind that causes race conditions no one can reproduce. Most people write async code. Very few understand when it actually runs. And that’s where bugs live. #JavaScript #NodeJS #Async #SoftwareEngineering #Backend
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most developers don't understand closures and it breaks their loops. classic problem: everyone uses let now so this fixes itself but the problem is still there, just hidden. here's why it happens: - when you use var > it's function-scoped not block-scoped. - by the time the timeout runs, the loop is done and i is 3. - all three callbacks reference the fix with let: let is block-scoped so each iteration gets its own i . but here's what you should actually know: - this isn't a JavaScript problem. this is a closure problem. - every function closes over the variables around it. - understanding that changes everything about how you debug async code, event listeners, callbacks. stop memorizing the fix. understand why it happens. #javascript #typescript #webdevelopment #buildinpublic #reactjs
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Hey JavaScript devs 👋 Did you know `this` can silently disappear in 3 very common situations? 1. Detaching a method from its object const fn = obj.greet; fn(); // this → undefined 💀 2. Passing a method as a callback setTimeout(obj.greet, 0); // this → gone [1,2,3].forEach(obj.process); // same story 3. Arrow function in an object literal const obj = { name: 'Pavel', greet: () => console.log(this.name) // this → global, not obj }; The fix is always one of three things: `.bind()`, a wrapper arrow function, or class field arrow methods. Which one bit you the hardest? Drop it in the comments 👇 #JavaScript #WebDev #Frontend #JS
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Day 5 Callback Functions 🔁 Understanding how functions can control the flow of execution is a game changer in JavaScript. Callbacks help us handle tasks at the right time, especially when working with async operations. 💡 Simple idea: “Do this task, and when it’s done, call another function.” Question: Where have you used callbacks in your projects? 👇 #JavaScript #WebDevelopment #Frontend #CodingJourney #LearnToCode
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🚀 JavaScript Output Challenge #4 (Trap Level) If you think you understand JavaScript deeply… this one will test you 👇 🧠 Question: (Check the code in the images) ⚠️ Rules: Don’t run the code Think step by step Focus on execution order 🤔 Try to answer: What will be the exact output? Why does it happen? What changes if we replace var with let? 💬 Drop your answers in the comments Let’s see how many get this right 👀 🔥 Concepts involved: Event Loop Microtask vs Macrotask Closures Scope (var vs let) 📌 I’ll share the detailed explanation soon #javascript #webdevelopment #frontend #codingchallenge #reactjs #nodejs
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Most React tutorials show basic folder structures—but real-world projects need something more scalable. Here’s the approach I follow to keep my projects clean and production-ready: 🔹 I separate logic by features, not just files 🔹 Keep components reusable and independent 🔹 Move all API logic into services (no messy calls inside components) 🔹 Use custom hooks to simplify complex logic 🔹 Maintain global state with Context or Redux only when needed 🔹 Keep utilities and helpers isolated for better reuse 💡 The goal is simple: Write code today that’s easy to scale tomorrow. As projects grow, structure becomes more important than syntax. What’s your approach—feature-based or file-based structure? 👇 #ReactJS #FrontendDevelopment #MERNStack #CleanCode #WebDevelopment #Javascript #NextJS #fblifestyle #IT #Structure #FullStack
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📌 Part 8 of 10: A lot of React bugs make more sense once you realize state behaves more like a snapshot than a live variable. That idea sounds small. But once it clicks, a lot of confusing behavior starts making more sense. Why logs can feel misleading. Why updates don’t look immediate. Why handlers sometimes “see” older values than people expect. Once I really understood that, I stopped fighting React as much. I started designing with it instead. What React concept took longer to click for you than expected? #React #ReactJS #StateManagement #JavaScript #FrontendDevelopment #Debugging #TypeScript
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What is a closure in JavaScript? A closure is a function that remembers variables from its outer scope even after that scope has finished executing. Why does this work? - `createCounter` runs once - It creates a variable `count` - The inner function “closes over” that variable - Even after `createCounter` finishes, `count` is still accessible Each time `counter()` runs: → it uses the same preserved state 💡 Closures are everywhere: - React hooks - Event handlers - Memoization - Encapsulation patterns They’re not just a concept — they’re part of how JavaScript manages state. #Frontend #JavaScript #React #WebDevelopment #SoftwareEngineering
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⚛️ React vs Vanilla JavaScriptVanilla JavaScript 🧩→ Direct DOM manipulation→ Code becomes harder to manage as apps grow→ State handling can get messyReact ⚛️→ Component-based architecture→ Reusable and cleaner code→ Efficient state managementWhen building small projects, Vanilla JS works fine.But for scalable applications, React makes development faster, cleaner, and maintainable.👉 It’s not about replacing JavaScript — it’s about using it smarter.#ReactJS #JavaScript #FrontendDevelopment #WebDev #Coding
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🚀 Understanding Asynchronous JavaScript – Behind the Scenes JavaScript is single-threaded, yet it handles asynchronous tasks so efficiently… ever wondered how? 🤔 This visual breaks down how browser internals — Call Stack, Web APIs, Callback Queue, and the Event Loop — work together to manage async operations seamlessly. 💡 Key Takeaways: • Call Stack executes synchronous code • Web APIs handle async tasks (setTimeout, DOM, etc.) • Callback Queue holds tasks until they’re ready • Event Loop ensures callbacks run when the stack is empty Mastering this concept is essential for writing efficient, non-blocking code in modern web development. #JavaScript #WebDevelopment #AsyncJS #EventLoop #Frontend #Coding
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You can simulate the cancellation by using https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/withResolvers and reject from an external location.