Mariusz Najwer’s Post

🚀 JavaScript Interview Question You Should Know ❓ What will be the output? console.log(a); var a = 10; console.log(b); let b = 20; 💡 Output: undefined ReferenceError: Cannot access 'b' before initialization 🧠 Explanation: 👉 var a Variables declared with var are hoisted They are initialized with undefined So internally: var a; console.log(a); // undefined a = 10; 👉 let b let is also hoisted BUT… It stays in the Temporal Dead Zone (TDZ) until initialized So accessing it before initialization: console.log(b); // ❌ ReferenceError let b = 20; 🎯 Key Takeaways: ✔ var → hoisted + initialized as undefined ✔ let/const → hoisted but NOT initialized (TDZ) #JavaScript #WebDevelopment #Frontend #CodingInterview #LearnToCode

Just published a new blog on Array Flattening in JavaScript 🚀 At first glance, it feels like a small concept… but once you go deeper, it touches recursion, problem-solving, and even interview-level thinking. In this blog, I covered: • What nested arrays actually are (with clear visuals) • Step-by-step thinking behind flattening • Different approaches (flat(), recursion, reduce, iterative) • Common interview scenarios and edge cases If you're learning JavaScript or preparing for interviews, this will be useful 👇 https://lnkd.in/gQgjYv54 #JavaScript #WebDevelopment #FrontendDevelopment #Coding #LearnInPublic #100DaysOfCode #Programming #SoftwareDevelopment

Day 85 of #100DaysOfCode Today I learned the Sliding Window technique, a powerful pattern for solving subarray and substring problems. Covered: • Fixed window problems • Variable window problems • Optimizing time complexity • Real interview patterns This technique is widely used in coding. #DSA #CodingInterview #JavaScript #LearningInPublic

🚀 Day 4/30 – JavaScript Challenge Solved: Counter II (LeetCode 2665) Today’s problem was all about understanding closures and how functions can maintain their own state in JavaScript. What I learned: 1.How closures help preserve variable values across function calls 2.Creating multiple operations (increment, decrement, reset) using a single function 3.Clean use of arrow functions for concise code Approach: I created a function that stores the initial value and returns an object with three methods: 1.increment() -> increases value 2.decrement() -> decreases value 3.reset() -> resets to initial value All of this works because of closure, where the inner functions still remember the variable n. Key Insight: Closures are powerful when you need to encapsulate data and control how it’s modified — a very common pattern in real-world JavaScript applications. Consistency is the real game here 🔥 Let’s keep building, one day at a time. #Day4 #30DaysOfCode #JavaScript #WebDevelopment #CodingChallenge #LeetCode #Closures #LearningJourney

🚀 Mastering the Sliding Window Pattern in JavaScript One of the most powerful techniques for solving array problems efficiently is the Sliding Window + Deque approach. Today, I implemented the classic “Maximum in Sliding Window” problem in O(n) time 👇 🔍 Problem: Given an array and a window size k, return the maximum value in each window as it slides from left to right. 💡 Key Insight: Instead of recomputing the max for each window (which is expensive), we maintain a Deque (double-ended queue) that: Stores indices (not values) Keeps elements in decreasing order Ensures the front always holds the max ⚡ Result: Efficient solution with linear time complexity — each element is processed once. 📚 I’m currently building a collection of algorithm patterns in JavaScript: 👉 https://lnkd.in/ej4fNeZs #JavaScript #Algorithms #DataStructures #CodingInterview #SoftwareEngineering #100DaysOfCode

#Hello #Connections 👋 #100DaysOfCodeChallenge | #Day52 🚀 Just Built a Random Password Generator 🔐 I recently created a Random Password Generator using HTML, CSS, and JavaScript. 💻 Features: Generate strong and secure passwords Includes uppercase, lowercase, numbers, and symbols Copy to clipboard functionality Clean and responsive UI ⚠️ Challenges I Faced: While building this project, I encountered some interesting issues that helped me improve my debugging skills 👇 Issue 1: Password not generating properly Solution: Fixed logic by properly using random character selection Issue 2: Copy button not working Solution: Used navigator.clipboard.writeText() correctly Issue 3: Weak password generation Solution: Ensured inclusion of all character types Issue 4: JavaScript not working Solution: Fixed script linking and DOM loading issues ✨ This project helped me strengthen my understanding of: JavaScript logic building DOM manipulation Event handling 🔗Github Link :https://lnkd.in/dAjqqBgK Code Of School || Ritendra Gour sir || Avinash Gour sir #JavaScript #WebDevelopment #100DaysOfCode #Frontend #CodingJourney

In my previous blog, I explored String Polyfills and common interview methods — understanding how JavaScript works behind the scenes. Today, I went deeper into another fundamental concept: 👉 The new Keyword in JavaScript At first glance, it looks simple. But internally, it performs multiple steps that directly impact how objects, prototypes, and this behave. In this blog, I covered: ✔️ What the new keyword actually does ✔️ Step-by-step object creation process ✔️ How prototype linking works ✔️ Relationship between constructor and instances ✔️ Common mistakes (like forgetting new) And most importantly 👇 ⚠️ Confusing parts developers often struggle with: Array() vs new Array() Object creation patterns Constructor return behavior If you’re preparing for interviews or want to strengthen your JavaScript fundamentals, this will clear a lot of hidden concepts. 🔗 Read the full blog here: https://lnkd.in/grUGpMqe Next up in the series: JavaScript Modules (import/export) 🚀 #javascript #webdevelopment #frontenddeveloper #programming #softwaredevelopment #coding #100daysofcode #learninpublic

🚀 JavaScript Array Methods You Should Know If you’re still looping through arrays manually, there’s an easier way 👇 These array methods can make your code cleaner, faster to read, and easier to maintain: ✅ filter() → Get matching items ✅ map() → Transform data ✅ find() → Get the first match ✅ some() → Check if at least one item matches ✅ every() → Check if all items match ✅ includes() → Check if a value exists ✅ findIndex() → Find the position of an item ✅ push() / pop() → Add or remove items 💡 Pro tip: In React, map() and filter() are used a lot for rendering lists and handling data properly. Mastering these methods can help you write better code and do better in interviews 💻✨ Which array method do you use most often? 🤔 #JavaScript #WebDevelopment #ReactJS #FrontendDevelopment #Programming #Coding #Developer #SoftwareDevelopment #LearnToCode #CodingTips

🚀 JavaScript Last-Minute Cheat Sheet — Perfect Before Interviews & Coding Rounds 🔥 Variables & Scope • "let" & "const" over "var" • Block scope matters • Avoid global variables ⚡ Functions • Arrow functions → shorter syntax • Default parameters save time • Closures = function + lexical scope 🧠 Async JavaScript • Callbacks → Promises → "async/await" • Use "try...catch" for error handling • "Promise.all()" for parallel execution 📦 Arrays & Objects • "map()", "filter()", "reduce()" = must know • Spread "..." & Destructuring simplify code • Optional chaining "?." prevents crashes 🎯 DOM & Events • "querySelector()" is your best friend • Event delegation improves performance • Debounce & throttle for optimization 💡 Pro Tip Understand concepts, not just syntax. Clean code + problem-solving mindset = real JavaScript mastery. Learn more From w3schools.com ✨ #JavaScript #WebDevelopment #FrontendDeveloper #CodingInterview #100DaysOfCode

🚨JavaScript Interview Question What will be the output? function greet(name) { if (name === undefined) { console.log("Hello, guest!"); } else { console.log("Hello, "+ name); } greet(); greet("Anas"); greet("Anas", "How are you?"); Looks simple... but there's a twist What will be the output? Why does the last call behave differently? Bonus: How does JavaScript handle extra arguments? #JavaScript #FrontendInterview #WebDevelopment #CodingInterview #ProductBasedCompany