Ahmed Khalil’s Post

🔥 JavaScript Devs — Why “Undefined” Causes So Many Real Bugs Hey devs 👋 One of the smallest values in JavaScript… Creates some of the biggest headaches 😅 👉 undefined often appears when: Missing API fields Wrong property names Unreturned functions Async race conditions 💥 Then suddenly: Cannot read property of undefined 💡 What helps: ✔ Optional chaining ?. ✔ Default values ?? ✔ Strong typing (TypeScript) ✔ Better API contracts ⚡ Senior insight: “Most runtime bugs start with assumptions.” Never assume data exists. What bug did undefined cause for you? #javascript #typescript #programmingtips #webdevelopment #frontenddeveloper #backenddeveloper #codingbestpractices #softwareengineering #jsbugs #cleanCode

TypeScript is not just "JavaScript with types". The more I use it, the more I feel types are design notes that the compiler can actually check. A bad type usually means one of three things: - I do not understand the data yet - The API contract is weak - I am mixing too many responsibilities in one place Today I refactored a response type from a loose object into a clear union: success response error response validation response The code immediately became easier to read. Good TypeScript is not about writing complex generics everywhere. It is about making impossible states harder to represent. That is the kind of code clients and teams can trust. #TypeScript #JavaScript #CleanCode

Node.js REPL is underrated. Need to test a function? Try a package? Debug a snippet? Just type: node Interactive JavaScript shell. No setup required. Simple tools. Powerful results. #NodeJS #REPL #DeveloperTools

Day 18/100 JavaScript Type Conversion Implicit conversion = hidden behavior Explicit conversion = controlled logic Great developers don’t just write code They remove uncertainty from systems That’s what I practiced today Database ID Mismatch example #100DaysOfCode #Theodinproject #javascript #webDev

JavaScript code runs inside a special environment called the JavaScript engine (like in a browser or Node.js). When you write code, the engine first reads it and understands its structure through a process called parsing. After that, the code is converted into a form (bytecode) that the computer can execute. During execution, the engine uses two main parts: the memory heap to store variables and data, and the call stack to manage function execution. It runs code line by line in a synchronous way, meaning one task at a time. For handling asynchronous tasks like timers, APIs, or events, JavaScript uses the event loop along with callback queues and Web APIs. This system ensures that tasks are executed smoothly without blocking the main thread, and finally, the result is shown in the browser or console. #JavaScript #NodeJS #WebDevelopment #Programming #Coding #Developer #Frontend #Backend #MERNStack #CodeNewbie

HOW NODE.js EVENT LOOP WORK ? Phases of Event loop in Node Js............................ See Diagram Test your JavaScript fundamentals with output-based interview questions focused on scope, hoisting, closures, and asynchronous behavior. 💬 Share your answer or reasoning in the comments. #JavaScript #InterviewPreparation #SoftwareEngineering #WebDevelopment #DevelopersOfLinkedIn #frontend #backend #coding #learning

If JavaScript runs on one thread… why doesn’t your app freeze during API calls? Most people think: “JavaScript is single-threaded… but somehow works like multithreading.” That’s not entirely true. JavaScript doesn’t do multithreading — it handles concurrency. Here’s the difference: Multithreading (Java): • Multiple threads run at the same time • Tasks execute in parallel • Output is unpredictable and interleaved JavaScript (Event Loop): • One thread only • Long tasks are delegated to the runtime • Results are processed later via the event loop So what’s really happening? JavaScript avoids waiting. Instead of doing everything itself, it: • Delegates slow work (timers, APIs, I/O) • Keeps executing other code • Handles results when they’re ready That’s why it feels like multiple things are happening at once. But in reality: → No parallel execution → No thread switching → Just smart scheduling Understanding this changes how you write async code. Read full blog: https://lnkd.in/gTmPSJqx #javascript #webdevelopment #programming #eventloop #concurrency

JavaScript tricks I wish I knew earlier 🔥 These save me hours every week: 1. Optional chaining - stop writing null checks const city = user?.address?.city ?? 'Unknown' 2. Nullish assignment - set default only if null/undefined config.timeout ??= 3000 3. Array flat - flatten any nested array instantly const flat = nested.flat(Infinity) 4. Object.fromEntries - turn a Map or array back into an object const obj = Object.fromEntries(entries) 5. structuredClone - deep copy without JSON.parse hacks const copy = structuredClone(myObj) 6. at() method - negative index access const last = arr.at(-1) These work in modern Node.js and all major browsers. No libraries needed. Share this with a junior dev who needs it 🙌 Shoutout to JavaScript Mastery, w3schools.com for keeping docs and tutorials world-class. #JavaScript #WebDevelopment #CodingTips #ReactJS #NodeJS #FullStackDeveloper #100DaysOfCode #SoftwareEngineering

Day 1/100 – Cracking Full Stack Developer Interview 🚀 Today I started with JavaScript Basics. - Explain About JavaScript Introduction - Difference between var, let and const - JavaScript data types (String, Number, Boolean, Object, etc.) 💻 Practiced: - Declaring variables indifferent ways - Tried simple operations using operators 🧠 Key Takeaway: let and const are safer than var because they follow block scope. #100daysofcode #javascript #webdevelopment #frontenddeveloper

🚀 JavaScript Event Loop: Your Async Superpower! 🌀 Confused how JS juggles multiple tasks on one single thread? 😵 Let's break it down visually! 1. Call Stack 📚: Runs your code line-by-line (sync stuff first!). 2. Web APIs 🌐: Handles async like setTimeout or fetch outside the stack. 3. Queues: • Microtask Queue ⚡ (Promises – VIP priority! Executes ASAP) • Callback Queue ⏳ (setTimeout – waits its turn) 4. Event Loop 🔄: Magic conductor! Checks empty stack → Microtasks → Callbacks. Pro Tip: Master this for smoother React hooks, Node servers, or any async magic! 💥 What’s your biggest Event Loop "aha" moment? Drop it below! 👇 #JavaScript #EventLoop #WebDev #ReactJS #NodeJS #Frontend #AsyncJS #CodingTips #Programming #DevCommunity #SoftwareEngineering #LearnToCode