JavaScript Prototypes and Inheritance Explained

🚀 Why Does null Show as an Object in JavaScript? 🤯 While practicing JavaScript, I came across something interesting: let myVar = null; console.log(typeof myVar); // Output: object At first, it feels confusing… why is null an object? 🤔 💡 Here’s the simple explanation: null is actually a primitive value that represents "no value" or "empty". But when JavaScript was first created, there was a bug in the typeof operator. Due to this bug, typeof null returns "object" instead of "null". ⚠️ This behavior has been kept for backward compatibility, so changing it now would break existing code. 🔍 Key Takeaways: null → means "nothing" (intentional empty value) typeof null → returns "object" (this is a historical bug) Objects (like {}) also return "object" 💻 Example: let myObj = { name: "John" }; console.log(typeof null); // object ❌ (bug) console.log(typeof myObj); // object ✅ (correct) 📌 Conclusion: Even though both return "object", they are completely different in meaning. 👉 JavaScript is powerful, but it has some quirky behaviors—this is one of them! #JavaScript #WebDevelopment #CodingJourney #100DaysOfCode #FrontendDevelopment

Day 4/100 of JavaScript 🚀 Today’s focus: Functions in JavaScript Functions are reusable blocks of code used to perform specific tasks Some important types with example code: 1. Parameterized function → takes input function greet(name) { return "Hello " + name; } greet("Apsar"); 2. Pure function → same input always gives same output, no side effects function add(a, b) { return a + b; } add(2, 3); 3. Callback function → function passed into another function function processUser(name, callback) { callback(name); } processUser("Apsar", function(name) { console.log("User:", name); }); 4.Function expression → function stored in a variable const multiply = function(a, b) { return a * b; }; 5.Arrow function → shorter syntax const square = (n) => n * n; Key understanding: Functions are first-class citizens in JavaScript — they can be passed, returned, and stored like values #Day4 #JavaScript #100DaysOfCode

Day 7/100 of JavaScript 🚀 Today’s Topic: Taking input in JavaScript. In browser-based JavaScript, input can be taken using: - "prompt()" - Input fields (DOM) On platforms like LeetCode, input is already provided as function parameters Example: var twoSum = function(nums, target) { // input is already given }; So the focus is on writing logic, not handling input However, some coding platforms (or local environments) do not provide inbuilt input handling. In such cases, we use Node.js Example: process.stdin.on("data", (data) => { const input = data.toString().trim(); console.log(input); }); This allows us to read input from the console Key understanding: - Platforms like LeetCode handle input internally - Other platforms and local setups require manual input handling using Node.js Understanding both approaches is important for coding practice #Day7 #JavaScript #100DaysOfCode

Day 2/100 of JavaScript 🚀 Today’s Topic: "let", "const", "var", hoisting and TDZ. "var", "let", and "const" are used to declare variables, but they differ in scope and initialization behavior - "var" is function-scoped and during the creation phase it gets initialized with "undefined", so it can be accessed before assignment. - "let" and "const" are block-scoped and are registered in memory during creation, but not initialized immediately. This leads to TDZ (Temporal Dead Zone) a phase where the variable exists in memory but remains uninitialized and cannot be accessed. Accessing "let" or "const" variables before initialization results in a ReferenceError. - "const" must be initialized at declaration and cannot be reassigned. - "let" allows reassignment but not redeclaration in the same scope. These differences make "let" and "const" more predictable and safer compared to "var". #Day2 #JavaScript #100DaysOfCode

🚀 JavaScript Output Prediction Challenge What will be the output? 🤔 💡 Important Behaviour: 👉 JavaScript executes code line by line 👉 The very first line throws the following: ❌ ReferenceError: a is not defined So in reality, the programme stops immediately and nothing else runs. 📌 Now, let’s understand what would happen inside the function (ignoring the first error): 👉 Before execution, JS does Hoisting (memory creation phase) Inside the function: var a → hoisted and initialized as undefined let b → hoisted but kept in Temporal Dead Zone (TDZ) (not accessible yet) 👉 Execution phase: "1:" → undefined (Because 'a' exists but not assigned yet) "2:" → ❌ ReferenceError (because b is in TDZ) After assignment: a = 10 b = 20 "3:" → 10 "4:" → 20 🔥 Core Concepts: JS has 2 phases → Memory Creation + execution. var → hoisted + usable as undefined let/const → hoisted but blocked by TDZ 💬 If you got this right, your JS fundamentals are solid 👇 #JavaScript #Hoisting #Frontend #CodingChallenge #WebDevelopment

🧠 JavaScript Hoisting Explained Simply Hoisting is one of those JavaScript concepts that can feel confusing — especially when your code behaves unexpectedly. Here’s a simple way to understand it 👇 🔹 What is Hoisting? Hoisting means JavaScript moves declarations to the top of their scope before execution. But there’s a catch 👇 🔹 Example with var console.log(a); var a = 10; Output: undefined Why? Because JavaScript internally treats it like: var a; console.log(a); a = 10; 🔹 What about let and const? console.log(b); let b = 20; This throws a ReferenceError. Because "let" and "const" are hoisted too — but they stay in a “temporal dead zone” until initialized. 🔹 Function hoisting Functions are fully hoisted: sayHello(); function sayHello() { console.log("Hello"); } This works because the function is available before execution. 🔹 Key takeaway • "var" → hoisted with "undefined" • "let/const" → hoisted but not initialized • functions → fully hoisted 💡 One thing I’ve learned: Many “weird” JavaScript bugs come from not understanding hoisting properly. Curious to hear from other developers 👇 Did hoisting ever confuse you when you started learning JavaScript? #javascript #frontenddevelopment #webdevelopment #reactjs #softwareengineering #developers

🚀 Understanding Prototypes in JavaScript (Simple Breakdown) 🔹 Every JavaScript object has a hidden property called [[Prototype]] 👉 It links to another object and allows inheritance 💡 Why Prototypes? Instead of creating duplicate methods for every object, JavaScript shares them using prototypes → saves memory ✅ 🔹 Example: toString() isn’t inside your object, but JS finds it through the prototype chain object → prototype → null 🔗 Prototype Chain (Search Order) Check the object Check its prototype Continue up the chain Stop at null 🔹 Constructor + Prototype Functions can use prototype to share methods: function Person(name) { this.name = name; } Person.prototype.sayHello = function() { console.log("Hello " + this.name); }; ✔ Method stored once, reused by all objects 🔹 proto vs prototype prototype → belongs to constructor __proto__ → belongs to object (actual link) p1.__proto__ === Person.prototype // true 🔥 Key Takeaways ✔ JavaScript uses prototype-based inheritance ✔ Objects inherit via prototype chain ✔ Memory efficient (shared methods) ✔ Core concept for interviews & real-world JS #JavaScript #WebDevelopment #Frontend #Coding #LearnToCode #Developers

🚀Day 30 — Scope Chain & Scope Types in JavaScript (Simplified) Understanding scope is one of the most important fundamentals in JavaScript 🚀 --- 🔍 What is Scope? 👉 Scope decides where variables can be accessed in your code In simple words: 👉 “Who can access what?” --- ⚡ Types of Scope 1. Global Scope 👉 Variables declared outside functions or blocks let name = "John"; function greet() { console.log(name); // accessible } --- 2. Function Scope 👉 Variables declared inside a function function test() { let age = 25; console.log(age); } console.log(age); // ❌ Error --- 3. Block Scope 👉 Variables declared with let and const inside {} if (true) { let city = "Delhi"; } console.log(city); // ❌ Error --- 🔗 What is Scope Chain? 👉 If JS can’t find a variable in current scope, it looks in the outer scope, then outer again… until global scope. This is called the Scope Chain --- 🚀 Why it matters ✔ Prevents variable conflicts ✔ Helps understand closures ✔ Improves debugging skills --- 💡 One-line takeaway: 👉 “JavaScript looks upward to find variables — that’s the scope chain.” --- Mastering scope makes closures, hoisting, and debugging much easier. #JavaScript #Scope #ScopeChain #WebDevelopment #Frontend #100DaysOfCode 🚀

🚀 **Understanding Callback Functions in JavaScript (In Simple Terms)** Ever wondered how JavaScript handles tasks like API calls, timers, or events? That’s where **callback functions** come into play 👇 👉 A **callback function** is simply a function passed as an argument to another function, and it gets executed later. 💡 **Why are callbacks important?** They help JavaScript handle **asynchronous operations** without blocking the main thread. 📌 **Basic Example:** ```javascript function greet(name, callback) { console.log("Hello " + name); callback(); } function sayBye() { console.log("Goodbye!"); } greet("Vikram", sayBye); ``` 🧠 Output: Hello Vikram Goodbye! 🔥 **Real-world usage:** * Handling API responses * setTimeout / setInterval * Event listeners (clicks, inputs, etc.) ⚠️ **But watch out:** Too many nested callbacks can lead to **"Callback Hell"** 😵 ➡️ Solution: Use **Promises** or **Async/Await** #JavaScript #WebDevelopment #Coding #AsyncProgramming #Frontend #100DaysOfCode